Probably Phoenix Wright. It's absolutely lovely.

Dead Rising on X360.

I didn't have any expectations but ended up enjoying it immensely. Dead Rising 2 as well.

Mass effect

Starlink actually became one of my favourite gaming moments of recent years. I only bought it for the star fox crossover but it does something that even the biggest releases often dont, its actually fun to play.

The Trauma Center series. I remember visiting a friend, who had some rented games with one of them being 2nd Opinion. I thought a game about surgery would be stupid, but I played it and found the game was actually pretty cool. I kept playing until eventually I felt I had to get this game for myself. Since then I've gotten all the following games and enjoyed them all

The same has happened with Kingdom Hearts and Wind Waker.

Ori and the Blind Forest was that game for me this gen. I went in thinking just another Metroid/Vania game and walked away saying this is one of the best 2d side scrollers i ever played.

FF7 was another, i had low expectations playing it especally at its slow start and the poor visual quality of the game back in the PS1 days. The game was that good i went out and brought the Original copy of the game for my PS1. Cost me over $150.

As a Final Fantasy, Koei Games, and JRPG fanboy, I didn't think this game would stand a chance.

World of Warcraft. It is my #1 game, but I truly didn't expect anything from it. Going to Walmart or wherever I got it from I looked at the back of the box as I did often with many PC games. Never played Warcraft, barely played Starcraft, didn't even know they were the same developers. It looked cool, so we decided to get it.

When we got home we had many unfortunate things happen. First was the install and download on dial up internet, that took 3 days. Next was the fact that it was an online game, so we had to set up accounts and stuff and pay $15 a month AFTER paying $40, no way anyone sane would do that. We finally get into the game and as you can imagine dial up internet sucks and could barely play the game, but to make matters worse my computer was basically the minimum specs or less. Many things sucked but in the end it was the greatest game I ever played.

Knytt Underground comes to mind, It was a ps+ freebie, didn't know anything about it, loved it. Music, art style, exploration all great.

Cavernous wastes for PSVR wins though. It looks like a bad Descent clone with rogue like gameplay I normally despise. It was very addictive, great retro music, amazing atmosphere and quite challenging gameplay.

Closure is a puzzle game that I did not expect much of yet ended up enjoying from start to finish. Same with Antichamber and Fract OSC, amazing games.

I tried ETS2 out of curiosity and ended up playing it a lot. Really getting into it by switching the radio stations to the actual country I was driving through. Early morning German traffic reports or Italian night time radio for the added immersion factor. The only thing missing was the radio going out through tunnels :)

Suikoden.  I had ZERO expectations for it.  The box art looked kind of lame and I just assumed it was a budget Final Fantasy since I'd never even heard of it.  I think I bought it for like $5 used from the rental shop.  I popped it in and thought, "yeah, this is a knock-off."  Talk about being completely wrong.  It had so much depth and personality.  I absolutely loved it and wish there was more of that kind of game.  

Valkyria Chronicles.  I bought my PS3 mostly based on anticipation for Uncharted 2 (which I didn't like) and The Last Guardian (heh).  I picked up Valkyria Chronicles as that cheapish game you buy with your console to play because you've gotta have something.  Ended up being one of my favorite games of the generation.

People mention Persona 5 but Persona 3 was a game I bought based on recommendations but that I didn't think I'd like.  It seemed weird and really niche.  I didn't care much for it at first, either, because I was trying to wedge it into my "JRPG" preconceptions and it just wouldn't fit.  Relationships?  School?  What the heck is going on?  The more I played, though, the more I wanted to play, and really started to love it for being its own thing.  

Ka-pi96 said: Final Fantasy 7. My dad brought it home one day after finding it in a bargain bin. So no expectations going in, never heard of it before and it was in a bargain bin, so how good could it really be? Well anybody who's played it should know that it's fantastic I do prefer FF 8-10. But I went into all of those with huge hype and expectations. FF7 is the only one where I expected nothing and ended up playing one of the greatest games of all time.

Oof, now that you mention it! I had a similar experience with FFVII when I was on a visit at a friend's house. He disliked the game because he couldn't get passed the first boss (facepalm). So that's when I fell in love with FFVII.