I'm not even remotely close to 100, much less 500. I only have 46. I don't have the attention span to be a completionist. I start a game, get halfway through the achievements, then a squirrel runs by and steals away my attention.
I have 72 completed retail and 48 completed arcade games with a completion ratio of about 90% and am constantly trying to finish up old games that I'm only missing a few achievements in.