My personal favorites from back in the day based on their simplicity of play and overall entertainment were (earliest) were Maniac Mansion, Castle Wolfenstein, Leisure Suit Larry on the oldest pre-ninetendo systems and Frogger, Mario and defender.
As the games progressed I love Contra Alien Wars, Zelda: Link to the Past, Super Mario Brothers and Castlevania
Now I lean toward the Resident Evil, Max Payne, Metal Gear series. Personally though, I DO miss the earlier game style where you could just pick them up and play them without it taking a week to get all the moves down, reading a manuel or having to relearn the controls again and where you were and what you were doing in the game because you haven't played it in a month or two.