Super Mario Brothers, Tetris, and Pac-man are still some of my favorite games, and they all have good, yet simple gameplay. I pick gameplay over graphics anyday.
It depends on the games in question. But there are more old games that are classics that new games. I don't tend to play classical games anymore so I'll have to go with new. But I love my classical games.
Don't get 'classic' and 'old' mixed up. Classics are games that are highly rated and loved through the ages. Old games are just games releases long ago.