I can't imagine a classic Stern being any better than Flight 2000. I'm new to the hobby, but own a Flight 2000. There is so much to do, drop targets, 2 spinners, neat ball lock/launcher, 3-ball multi-ball, controlled light switches. The game can play pretty fast if you get the pop bumpers and sling shots working well.
If there are classic Stern machines better than Flight 2000, then I need to play them and add at least another one to my collection! I'll be on the lookout for buying opportunities for sure.