Not a problem. Okay...since I've got some more time now, I'll continue adding...
(note: these are ranked in order of community rating. I might personally disagree a bit, but proably not too much)
-rogue legacy: a roguelike castlevania adventure. The "each time you die you continue with your heir" gives hilarious results.
-coo, serve, delicious: one of my all-time favorite games. The sequel is even better, but I'd start with this one (also because it has lower specs)
-braid: another classic. I'm not sure how well it plays on lower end PC's, though
-race the sun: endless racing. Pretty soothing, despite that it can get pretty brutal. visuals remind of star fox
-guacamelee! gold or street fighter 2 turbo...something edition: a hilarious Mexican-themed metroidvania. It's worth it jus to try if your rig can hold it
-melody's escape: hmm...okay, it has good music, but I find it rather "meh". IIRC you can use your own music in this rhythm game, though
-unepic: a metroidvania that both hommages and parodies video games
-world of goo: everything by 2D boy / tomorrow corporation is at least interesting. This one's an absolute must, though (IIRC, I managed to play this smoothly on a single core PC)
-140: an abstract platformer that has no text whatsoever. Somewhat rhythm based. Not exactly long, but it's certainly fun
-Stanley parable: erm...this MIGHT be too taxing, but then again: it doesn't require much reflexes. It's a bit overrated to my liking, but I know a good game when I see one.
-steamworld dig: a platformer where your goal is simply to DIG DOWN. Nonetheless, this gae has more variety than you'd give it fcredit for
-fez: easy to hate the developer, but don't let that distract you from the fact that the game itself is charming and clever (not so unique now anymore, though)
-human resource machine: another 2D boy game. This one...teaches you assembly-like programming
-renowned explorers: I usually can't stomach turn based RPG'S, but this one has "verbal" fights. it's still less my liking, but if you love these games...you might be interested
-robot roller-derby disco dodgeball: I swear this is just a UT2004 clone. Then again: that means it'll might just run smooth enough on your computer
-infinifactory: I...honestly have to advise against it if you can't test this. The game is great if you like puzzles (apparently like factorio, but I haven't played that one yet), but it is in full 3D.
-runner2: future legend of rhythm alien: an endless runner. Correction: a pretty fun one
-Duet: premium: this should be near the top of the list. It runs on anything (I even finished it on my phone), and has some of the best video game music ever created. Also: soothing
-diamo XL: one I recently stumbled upon. It's incredibly simple in concept (color the rhombus and the cross within without getting hit) but oh, so addictive.
-Jazzpunk: IIRC uses the unreal3 engine, so be wary. But this is the best comedy game since monkey island. And it even rivals that. It is, however, a walking simulator, so...yeah.
-edge: abstract isometric platformer. Pretty fun, but...while some interesting level design, not the best game ever
-faerie solitaire: why do I even play this game? It's a solitaire game (place higher or lower on the stack) with fantasy elements. It's fun and addictive, but overall...average
-parkitect: sigh...I have honestly no idea how well it'll run (once you start making big parks, of course). But this is basically rollercoaster tycoon.
-contraption maker: to my horror, this generation of gamers doesn't know what the incredible machine is. Well...this is by the same makers. And it's awesome
-roundabout: sandbox game where you play a limousine that constantly turns. It's as hilarious (and hard) as it sounds. Also: best cutscenes since original command & conquer.
-pac-man 256: there are a few modern iterations on pac-man. I like this one the most: in an endless maze where you run away from the ever-crumbling chaos behind you
-the bridge: while I think this Escher-like puzzler could be faster paced, I concede it's good. Not great, but good.
-train valley: if you calmly wanna build some railroad tracks and let trains pass just to marvel at them in passing, then this game isn't for you. Everything costs money: tracks, letting trains wait, the cargo diminishes...But if you get in the concept of quickly laying tracks (pretty much with the train directly behind it) and letting them ballet next to each other JUST avoiding a crash...then I fully recommend this game.
-tales from space: mutant blobs attack: yeah...I had fun with this one. In origin, it's not that special and not hard at all (you are a blob that absorbs stuff), but the humour makes it more than decent. I mean...you constantly grow in size, which is basically that the scenery constantly shrinks. And...that goes places.
-stealth bastard deluxe & stealth inc 2: still my favorite stealth games of all time (sorry, mark of the ninja). clever level design as well.
-eldritch: this...is one you might hate. it has 3D that reminds of the original wolfenstein 3D, randomly generated levels and pretty overpowered enemies. But this isn't a shooter but a roguelike. and those monsters have to look like that because Cthulhu mythos. As said: you like it or your hate it.
-owlboy. wow...I thought this'd be much higher. But ey: hand drawn metroidvania goodness is good.
-Toki tori: don't let the cutesy looks fool you: this is a puzzle platformer with a heavy emphasis on the puzzle part
-Ovivo: my most recent played one. Haven't really made up my mind on it. It's an interesting take on VVVVVV and has some flow to it. the design is pretty bizarre, though.
-blackhole: I...really need to play this more. like some other platformers (ovivo, vvvvvv), it messes with gravity. The level design is almost bizarrely good. I mean...you can probably skip through most of the game by just collecting one gem in each level, but if you really want to go to collect all three, it's like these simple concepts have depths you really hadn't expected.
-nightsky: this is one of those "flow racers". it's about building up speed and changing your charging just at the right angle. It's not brilliant, but certainly very good
-crashlands: if you want don't starve without the difficulty and with humor instead of nightmare before christmas: crashlands is your go to game
-teslagrad: a hard bargain: I don't like this game but I honestly can't say why: graphics are good, the puzzle in the puzzle platforming is good, level design is decent...it might be just the time period in which I played it, but I just couldn't get into it.
-expand: an abstract game that has you avoiding the walls. It's okay.
-insanely twisted shadow planet: a metroidvania where you play a flying saucer on a planet made of spikes and thorns
-the final station: okay, I played this one after watching the zombie movie "Train to Busan" (which is excellent!). The game is...probably not as good as I remember, but meh...I liked it.
-element4l: like nightsky: a game where your goal is to build momentum. This one's cute, charming and incredibly fun. A bit frustrating at times as well, but very good (should've been much higher IMHO).
-the static speaks my name: okay...just play it. It's free and only takes ten minutes. It's great...but the very opposite of "a fun game" (basically: it's the very essence of a true horror game).
-mushroom 11: I really hope this runs well on slow machines, because you'll need fluidity. In this game, you play a blob that you "move" by pointing your mouse at (which removes that part of the blob and causes it to grow in the opposite direction). Very interesting and creative. Not sure if it's for everyone, though
-hero siege. In a way, I don't like this game. Like binding of Isaac, it has crude graphics and the classes are ridiculously unbalanced. Nonetheless, the next thing I knew it was hours later.
-sproggiwood: if you liked crypt of the necrodancer with the bard: this is, in a way, even better. This is currently one of my go to games on android
-type: rider. erm...I don't know if you're interested in learning about book printing, but this one mixes that educational thing with platforming. I liked it...but can't say whether you'll agree.
-pix the cat: a trippy experience: as a cat you've got to collect eggs in a maze. It's against the clock
-gone home: a walking simulator of a girl (or boy...that part isn't important) that comes home and finds it empty. Except for a gazillion notes that tell what has happened since you were gone.
-chime sharp: a very addicting tetris/limines -ish kind of game: lay down blocks from above; once you've got a rectangle big enough, it'll be marked to be deleted. "Delete" as much from the ground as you can.
-balancity: probably the worst game I still suggest: build a city on a plate that hangs across a volcano. It mixes stupidity with city building.
-and yet it moves: like the vvvvvv clones: you can rotate the entire level. Pretty fun game
-freecell quest: okay...if you don't like freecell (the card game), then DON'T play this game. This is an RPG where all battles are done through freecell matches. It works...very good, even. But damn, things can drag on in the late game.