2D Mario Platformers
Monkey Island
Metroid
Mass Effect
Metal Gear Solid
Monkey Island and Mass Effects are newcomers for me, as I've been only recently introduced to them. Metal Gear Solid, in the past, would've at the top of my list, but I absolutely hated the direction they took with MGS3. MGS4 was better, but it had an even more convoluted storyline than MGS2, it was dull and FULL of cutscenes, and it had the same overly complex controls of MGS3. MGS1 still ranks as one of my favorite games ever, but I stopped caring about the series.