This is easy.
1. Persona 3. I found P4 to be too bright. It has a happy ending, where P3 does not. I bought a 50 dollar custom made metal evoker just because.
2. Mass Effect 2. Ordinarily I would prefer 1, but looking back at the others, 2 stands out.
3. Disgaea. Of all the games in this list, I probably spent the most time on this. I still have 6000 levels to go for Laharl.
4. Sonic Adventure. Not only is this my first game, but the most memorable. When I was 3, I broke my dreamcast when I got frustrated on the last boss. I had to buy it for 360 just recently.
5. Dark Cloud 2. The original is within my top 100 games, but the second improved so much.