Metal Gear (series): Honestly, I have never found a better stealth game. Yeah, there's Theif, but it just felt like it was missing something. Plus, the reboot was kinda not great. Not to mention there's the whole move away from true Stealth to Stealth/Action (looking at you, Blacklist) which really pisses me off.
Metal Gear Rising: Revengance: I have never enjoyed a spectacle fighter as much as Rising. I mean, just the fact that you can literally cut almost anything in the game was a huge plus for me. The nonstop over the top robot cyborg ninja vs other robot cyborg ninja (or buff US senators) action was just overkill at that point. Pls, Platinum, I can only enjoy this so much before my mind blanks out from all the fun.
Starcraft II: I really, really hate this game. I really do. If it's not fucking Protoss and their bullshit cannon rushes all over my fucking natural, or fucking Terrans and getting fucking Reapers at five minutes, or fucking Zerg and we all know what they like to fucking do. But despite all that, I also really love this game. To use a certain famous quote, I just love it when a plan comes together. Like when my opponent has no detectors and my Dark Templars fuck up their entire base, or when my opponent plants their army next to their wall and everything gets baneling busted, or getting fucking nukes as Terran, because their nukes, those will always be awesome. I've never played a more intense or more enjoyable RTS than Starcraft II, mostly because I haven't played OG Starcraft, but all other RTS that I've played have seemed like absolute trash compared to SCII.
Halo: Combat Evolved. This game was everything a First-Person Shooter should be. Weapons were simple and easy to understand, as were vehicles. The story was simple yet engaging, and the plot twists were appropriately timed and excellently executed. The gameplay was both fun and challenging. And the end of the game, racing a Warthog across the spine of the Pillar of Autumn as literally everything is exploding around you... never since has a final mission in an FPS been anywhere near as intense.
War Thunder. There's really only two other games in this genre at present time (World of Tanks/World of Warplanes) you can take any other game in existance, any one, go ahead, choose. It will still be better than WoT and WoWP combined. War Thunder isn't exactly the best game ever, but it is the best F2P multiplayer WWII combat sim, so yay for winning by niche genre!
Pokemon Generation III/Generation III reboots: There's nothing that really needs to be said about these ones. It's Pokemon. And it's the best Pokemon. Fight me if you want, my Swampert will beat the shit out of any starter you want. Charizard? Waterfall. Typlosion? Earthquake. Empoleon? Superpower. Serperior? Ice Punch.
Ace Combat (series). Oh man. What can't be said about these games? I'm just going to leave this for you all to listen to and tell me that Ace Combat isn't a good series. http://youtu.be/WSuMXlkd5jQ
EVE Online. Hardcore Internet Spaceships. Enough. Said.