I'm a big fan of Hunter X Hunter Online. http://hunter.unigame.me/
By far the most time I have spent on my 3DS is in that game.I can achieve my desire, through each level has a sense of accomplishment.
I have a ton of games in my Steam library from years of sales and stuff, but anymore I really only play League of Legends. I only play two or three nights a week, but a lot of my friends play, so it's a nice way to stay in touch with them and just have fun after a long day at work and school
Mostly football games are my thing, I play on daily basis without missing my game time schedule because it helps me keep sane with all the stress and pressure one have on daily intervals. PES and FIFA are my favorite game for now, I play them both on PC and play station console.
Lately I've really gotten into Sunless Sea. Yes, I know that it's a bit older game already (2-3 years I think?), but despite the rather simplistic gameplay the drawn graphics and especially the depth and variety of the story gets me! I truly feel like I'm on an sea adventure with that game, highly recommended for people who are not afraid of slow-paced, text based games!