I picked up Batman, Arkham Asylum on steam a long time after release when it was on sale. I always thought video game tie in to other franchises were pretty bad, and Batman seemed like the kind of title that would get a below average game. What I got was the most surprising turn of events I've experienced in a long time. The combat was great and fluid, the stealth was great (maybe not in a "real" sence, but they took gameplay first and it worked out). The gadgets were awesome, the riddler trophies were fun to find (not like the other two, were they felt like they were there just be there). This game got me so entrenched in batman lore I'm probably sold on every Arkham game forever, even though the charm and small scale is lost in the new ones. Had one dissapointing boss (killer croc) but everything else was a joy.
Another game that I got on a steam sale for cheap way after the game was made was Dark Souls. I'd heard of demon souls before and knew it was a hard game, I thought from what I'd heard it was like a super hard Devil May Cry game, but eventually I heard that the lore in Dark Souls was cool so I bought in sale. Dark Souls was the most astonishing game I've ever played, it blew me out of the water with its slow and methodical gameplay, the atmosphere, and the absolute freedom the game actually gave a player. It was basically one of the games I'd thought in my head (gameplay wise) and to see it come to life before me with an environment and multiplayer specifically built to just reinforce their core message was brilliant. I remember the first time I found a shortcut I just loved it. Superb level design, enemy design, just very well designed all around, the PC port was bad at first but I never experienced it and in stereoscopic 3D it's one of the best looking games I've ever played. Just like with Arkham games I think Dark Souls 2 lost a lot of what made Dark Souls amazing instead of just really good. I'm tempted to buy a PS3 just to play Demon Souls now.