Wizardry: As a part of Brooks' series of films, it was a negative sign of things to come, and as a film on it's own it's an immature piece of comedy relying on simplistic slapstick humour. There are worse films out there (Brooks' "Robin Hood: Men In Tights" for one), but that doesn't give "Spaceballs" an excuse for what it is. "Spaceballs", put simply, is a film that every child will love, but which eventually we will all grow out of.
spindown: Thank you, finally a sane person. I've never understood why this cheap piece of childish slapstick humor is considered a cult classic by so many people. I actually find it embarrassing to watch.
I enjoy Spaceballs for the very reason that it is simplistic, slapstick humor. A guy can be wealthy enough to afford filet mignon for dinner. But every so often, he just wants a hamburger. Same idea with movies. Every so often, I just want to watch something stupid and mindless. Spaceballs fills the bill.
Edit: And kudos to those who mentioned Outland. It's not in my top five; but it makes my top ten.