There are a lot of different genres of games, some more popular than others, and some more thoroughly explored than others. What is a genre you feel hasn't gotten the love it deserves, or just hasn't been used at all lately?
I've been disappointed by most platformers lately, both fully 3D and side-scrolling, and it might be because there are fewer devs making these games. I haven't played a 3D platformer as good as Banjo Kazooie or Donkey Kong 64 since, well, either of those games. Even Yooka-Laylee, which is made by many of the same people from Rare who made those games, felt like mostly a letdown. I've heard a Hat in Time is similar and better, but that's two recent games I can think of total. Not much representation. Most (non-combat-oriented) side-scrolling platformers feel incredibly un-challenging lately. Donkey Kong on Gameboy, DK Country, Yoshi's Island; those were all exciting adventures that made you use your brain and your reflexes. The few side-scrolling platformers I've found to play lately have been boring scripted tours with no sense of exploration. I'm talking about that recent Prince of Persia or that Little Red Riding Hood platformer that came out a few years ago. I literally can't think of anything else of that (non-combat-oriented) platformer genre that's been big in the past half-decade, and anything I do remember playing was not a good represenation of the genre as it was and as it could be.
*looks left* *looks right* Second person shooters. People have focused a lot on first and third person, but not second. Yes I got the jokes.
3D 'flying'-on-rails adventure (aka the NiGHTS games' style of play) Those 2 games are the only 2 I know of that do that! Niche game genre/play, but it can be done well?
