Well since it's been bumped, I may as well throw in my 2 cents.
My game lists are pretty intense. I have one "Favourites" list that I tell my guests to use, and I put all my favs in it, my wife's favs, and the usual suspects (TMNT, X Men, Donkey Kong, anything I think may get requested)
I also have the special controls like trackball games and lightgun games sorted - saves time when someone wants to play a shooter game or whatever.
Off the top of my head:
Classics
Beat Em Ups
Driving
Breakout
Maze
Puzzle
Flying
Favourites
Trackball
Lightgun
Sports
Shmups
VS Fighter
XXX
I may consolidate my puzzle, maze, and breakout into the puzzle category. Probably a good 90% of games that people want to play at my house are in the favourites list, and 80% of that is either Golden Tee or ShuffleShot.