Depends on what you mean by "collector". If you mean a serious collector who isn't afraid to spend money on nice games, then something like a Tempest, Star Wars, Robotron, etc is a must have. Everyone has a Ms. Pac, Galaga, Centipede it seems, so there's no big rush to get one. And if that's what you like and space is limited, just put a 60-in-1 in there for those common ones.
Now, if you're just talking about the typical "I want an arcade game" guy, then that guy has to decide if he's more interested in title or price. If he wants specific titles, then save his money until he can get a nice one. If he wants cheap games, then just watch CL and look for deals. Don't worry if the cheap ones aren't what you want most right away. Get them, fix them (if necessary), then use them to trade or sell when the one you want comes along...