Kingdom Hearts-Amazing combat, decent story and boss fights that were challenging and fun (Sephiroth in both games and Riku)
Batman Arkham Games Combat is awesome, stealth is so much fun, and nothing makes me giggle harder than stealthing around an area, picking off guards one by one and stringing them up for their last screaming comrade to see before a black shadow blocks out the last light source and covers his vision. Fear. I love these games!
Serious Sam I've yet to play 3, but 1 and 2 are so cathartic and so much fun with a friend Co-op. Nothing tests a friendship like being on Serious Difficulty and frantically trying to cover the other player as they hunt for ammo and armor and then switching places while whittling the enemy hordes down to nothing. Good times
Diablo Yes, i'm going to get crap for this but I thoroughly enjoyed 3. Not the RMAH or the AH. I have personally only used them 1 time and that was to help a buddy replace his weapon. I enjoy the group aspect. Plus taking down Diablo on Inferno with my monk and my buddies under-geared Barb was insanely fun. I was constanly refreshing my cooldowns and popping my heal+Invincibility spell whenever it came up to keep us both alive. 2 still is one of the few PC games i've spent over 500 hours on. It consumed my time while i was recovering from a broken bone.
Star Trek Armada These are brilliant RTS games, and everyone should play them. Story lines are good and feel fleshed out, unit management/creation is satisfying almost to the point of being illegal and multiplayer skirmishes online are an indecent amount of fun. LAN gaming nights, i still pull these amazing games out and my friends and i will be up til the wee hours of the morning clashing and harvesting materials and making desperate grabs for uncharted parts of space in the hopes that we can mine 300 more dilithium to build the lynch-pin of our armada.
Devil may Cry 1-3 No, i didn't enjoy 4 all that much. The backtracking for the last half of the game as Dante wasn't fun or engaging for me. Nero was a stupid main character and honestly it bored me. 3 has the best combat system for me (Trickster all the way) and 1 and 2 were some of the first action combat games i ever played on my PS2.
EDIT:
Also, i just remembered:
Ys I love these games, the combat, the story, the characters, the weapons and monsters, the environments. The very first time i played an YS game was on my PsP. I spent so much time just running around and beating the be-jesus out of monsters and the boss fights require skill and timing! ITS INCREDIBLE. Granted, going back and playing 1 and 2 makes me feel stupid. You run into enemies to damage them? Thats just not a good idea. Still fun and the story helps it along. But if you haven't played any of the YS games:
GO.
DO.
IT.
RIGHT.
NOW.