SMT Nocturne caught me completely off guard.

Splattoon and just cause 2

Many, though the first one that comes to my mind is call of duty modern warfare.. amazing campaign and multiplayer. I still play it from time to time

For me - totally Skyrim. I had never played a Elder Scroll game, nor a completely open world game (they way that it is.) I still fire it up from time to time years later.

Another one would be Alan Wake - never thought I would go back, play, and collect everything.

Runner up would be PacMan (Championship DX). I enjoyed the arcade, but was never very good - nor cared about being good. But this game is addictive!

I went into Xenoblade Chronicles for the Wii knowing I'd like it but wasn't sure if I'd care enough to complete it.

I was completely blown out of the water.

Pokémon Picross. I expected to have around 5 hours of fun, not playing that game like 50 hours.

Persona and Growlanser

My first Monster Hunter game (Tri, on the Wii.) I knew I wanted it (I got it when I was little) but I didn't expect to love it as much as I do now. It's one of my favorite franchises.

Yes indeed. Legend of Zelda Wind Waker. Was looking for somthing new to play on the Gamecube (which I had purchased because of its insane discount price) and the guy at the game store suggested Wind Waker..He said you will love it. I thought no way, this is for children. Looking back it is among the best game I have ever played...

Persona 4 Golden. I played that game until I fell asleep then woke up next to my Vita to play it again.