Successful works get sequels, and the amount of things that eventually get run into the ground has spawned any amount of phrases (difficult third album, similar things for TV series, books might not land a trilogy, only as good as your last...). This can lead to people abandoning a franchise while the corporate overlords are content to run it into the ground. Occasionally though the money gets low enough, as does the corporate oversight/meddling, that people responsible for making it, which may well be fans of the "good" entries, can turn out something that merits an actual look. Or for those collecting cool kid hipster points then as they got famous is good, before they got famous is better but being a fan after they were famous... there is the good stuff.
For instance Heroes of Might and Magic, while the author of this piece is one of those dangerous subversives that reckons 2 gold is the height of the series rather than 3 then there are those that tell me the latest entries are possibly worth a look, especially with mods. The Tony Hawk games for many went downhill rapidly after 4, however I can safely say that the classic mode of American Wasteland did pretty well actually and naturally many will be quick to point out the recent remake of the earlier titles was very nice, though those looking to get into the series today I will probably point at the THUG pro mod/collation. Or indeed EA's Skate series which was sadly never allowed to be run into the ground like so many other EA franchises; did any of the more recent Call of Duty titles or Need for Speed titles do anything for those that might have dropped out during the PS3/360 era or indeed PS2 era?
This can include games that never saw sequels appear outside a region, in this case the once popular Wizardry series (one of the foundational games/franchises in dungeon crawling RPG) is a rare case of gaming Big in Japan (normally a fate reserved for musicians). It stopped being made in 1992 in the west but has continued on in Japan to this day (titles on the GB, GBC, GBA, DS, PS1, PS2 and PS3 as well as many mobile phone entries) having not really come outside it save for a few spinoffs.
To that end share a pick or two of games in once popular or influential franchises that got run into the ground, however later sequels actually had something worth considering when most dismissed them. If you are going to include a spinoff then try to make it at least vaguely in line with the base games; Summon Night and Summon Night Swordcraft Story are close enough, Street Fighter to Super Puzzle Fighter is pushing it a bit.