I feel as if many of the 80's cartoons have great theme songs.
Examples:
Robotech - Sweeping orchestral score. Let's you know from the jump that you're not watching an episodic series, but a serialized space drama.
Transformers - The lyrics tell you everything you need to know. I also suspect that the S1 intro had every single robot available as a toy in there.
Jem and the Holograms - Makes you aware you are in for something truly truly truly outrageous.
And this was from the 90's, but Mighty Morphin Power Rangers had a pretty kickass theme
(It also works great as a mashup)
As for bad ones, I'll say all the NCIS themes except New Orleans.