- The characterisations are more complex. In the original cartoons Leonardo is the gullible one that points out the obvious, Raphael is the smart-ass with the wisecracks, Donatello is the computer science nerd, and Michelangelo is the party dude. In the new cartoons Leonardo is the spiritual one who enjoys solitude and struggles with his role as leader, Raphael is the brooding, passionate one who struggles with his anger, Donatello is still the intellectual one, but often he excludes Michelangelo from his experiments, even though Michelangelo (while being impulsive and foolhardy) is actually smarter than everyone gives him credit (he has often used his brain to get the whole crew out of dicey situations).
- The drawings and animation are better (IMHO, at least). It looks grittier in a more consistent style.
- The storylines are tighter and better conceived. Sometimes the stories go completely crazy, but no crazier than the old ones, and with more plot-twists. My favourite episodes were probably the earliest ones, but the cool thing with the whole series is that it leaves things for a while, then comes back and builds on them when you least expect it.
- It effectively combines the stories of the old cartoons, the comics, and the movies. I think by 'rebooting' the series (a la DC Comics' Infinite Crisis) they had the chance to marry all the elements coherently.
Having said that, the original series was very cool - I watched it every weekday at 4:30pm after school - and I was pissed when they finally took it off the air. I've got about 50 action figures still as well, complete with all the weapons (though suffering the casualty of April O'Niell, who is missing a leg due to my sister's antics as an infant). I LOVE the TMNT movie (the first one, not the rest), it is a tight, 1hr 20m piece of cinematic gold. It is always in my regular viewing rotation as of a few years ago when I dug it up again (I went over all my friend's houses and showed it to them - we loved it). Has it been released on DVD? My video's sound quality is really starting to suffer...
I'm up for a new TMNT movie, so long as it's as well-done as the first one.
How good was it when Chief Sterns asks the gang members at the end if they knew anything? One of them pipes up and says "Check out the East warehouse over on Lairdman Island, you'll find your answers there..." Did anybody get that reference?