SatAM is the one sonic series I really liked because it had a lot of what I was looking for well balanced characters, storylines, and action it all fit together and in a strange way stayed true to the spirt of the games.
Adv of Sonic I thought was pritty good, not exactly a high point in my book, it went with a comidy premise which actually made it work because it had a fun admisphere like the original Sonic games. I'll never forget that catch phrase "I'm waiting." there is something about the way he says that that makes it funny. Though it wasn't perfect, there were times I felt that show tried a little too hard to make us laugh which resulted in a few lame or retarded jokes, and some plotlines were out of place (or at least that's how I felt). But still this show has a speical place in my heart.
Sonic Underground never and won't bother to due to the negitive vibe I heard.
Sonic X: Liked that one to balanced in characters, comidy and action. But I had only one problem with the show it has a balancing issue that holds it back. The subplot which is the Chris character kinda got in the way sometimes which can make watching this show a bit frustrating where I'm thinking cmon I don't want this guy anymore I want Sonic and the rest. Though further along Chris and a few other human characters with him become mere background characters after a while thankfully. But like this show all the same.
There are some video games that can make good animated shows and Sonic is one of them.