Beat'em ups & JRPGs. Well, I can still put myself in the mindset to play and enjoy a beat'em up, but I still find myself looking at the flaws and remembering why they aren't top tier for me any longer. JRPGs became too samey for me after a while, but I'm back to liking them (just not all of them, or even most).

Strategy games. Maybe because I just got bored of them.

Genre: Sandbox games.

Culprit: Watchdogs.

Ubisoft suddenly doing a yearly release of Assassins Creed did not help either.

Fighting-games. During the SNES and PS1 eras i played Street Fighter and Tekken a lot, but after that i didn't play them for the longest time and when Street Fighter 4 was released on PS3 i bought it and it just didn't do it for me anymore

Used to play SF2, mortal Kombat and Killer Instinct in the arcades and on home consoles.  It was something new at the time, and the arcade scene was exciting.  Now there are a million games like that and it's just not as fun playing online as in person.  

Fighting games are just too simplistic to still be enjoyable for a long period of time. They were interesting on the SNES, but by the PS2 they had definitely overstood their welcome.

Shooter games are too simplistic as well. Any game where the purpose of just shooting things on the screen are just simple and boring.