Project A-ko, and the sequels were pretty good. The first movie had the best animation, and in terms of quality, it's 1, 4, 3, 2, though they have continuity between the movies, so it's best to watch them in order. Project A-ko Grey/Blue series was only okay, and in an alternative continuity, and can be skipped.
Tenchi Muyo! was pretty funny. I prefer the first few "movies", the second set of "movies" weren't as good. The tv series was good, but also in an alternate continuity.*
Demon City isn't bad if you're looking for a bit of the 'ol ultra-viol.
*What is it with Japan and reboots? Probably the same mentality that involves giving RPG enemies a new paint scheme and treating them as a new enemy type.