I watched a couple Jontron movies, and these really aren't reviews in the slightest. It's just him being funny all the time. If you don't already know the game in advance, then you'll have no idea about it later.
On the "always finish the game"...that really depends on the game. Games like race the sun, bejeweled, sim city or flappy bird have no end to get to, and quite some roguelikes are near-impossible to finish (in Don't starve, I usually die before finding the gate to start the actual adventure mode). And games like Lyne have 676 levels (as well as an unlimited supply of daily generated ones), even though you know all the mechanics after the first three or four levels. Have fun finishing those.
As a general rule of thumb, I'd say that it goes for story-driven games, but even there...I don't want to be the reviewer who has to spend who knows how much just to be able to finish Candy crush saga.
(okay, you could argue that isn't story-based, but hey...I'm just pointing out that you can't go with that).
: I don't see how games that haven't been talked about would pose more of a challenge. I "review" games as soon as I'm tired of them, but the only reason I look at other reviewers is to see if they're pointing out things I don't care about (like how multiplayer behaves in a singleplayer-oriented game). And that's just that I then put in my text that I haven't tested that. Nowadays, it's pretty hard not to find at least some games you can compare it to*. All in all, if you have an opinion of a game (and you wouldn't be reviewing it if you hadn't), then those words should come automatically. Especially if you're showing sound and visuals.
*jazzpunk is one of those games. So I just pointed out that it's somewhat of a first person point 'n click game with the absurd humor of wario ware games.