I don't have a problem with your opinion, I just don't happen to share it. Superman pwns all.
And I don't think it was ever the producers' intention to do Legion without Superman. As Blackstar previously pointed out, Superman Returns came out the summer before LoS' debut, and many people wouldn't have bothered with the show if it didn't have a big name superhero featured in it; these same people wouldn't have bothered with Teen Titans if Robin hadn't been there, most people outside of comic readers had no idea who Starfire, Cyborg, Beast Boy and Raven were before the TT show started up. Supes has always been an integral part of Legion (heck, the Legion was introduced in a Superboy comic), so it's only natural that Supey be in the show. I'd have a hard time picturing the show without Superman. It would be like doing a Brave and the Bold show without Batman.
BTW, there was an episode about the Legion's forming in season 2, "Origins", so there was no need to make that the focus of the entire series.
I'm one of the few people on this board who actually liked FF:World's Greatest Heroes. Some of the fight scenes could've been better, I'll give you that, and I disliked those candy-white and orange colored costumes that the team wore, but I have to disagree with your assessment of the character portrayals. I thought all of the characters were executed well; this show was my personal favorite portrayals of Susan and Johnny Storm. At least in WGH each of them had a personality, rather than the ciphers they were in the Marvel Action Hour version. I didn't find Sue annoying at all (I'd rather see her the way she was here than as the blandly virtuous damsel-in-distress), and Johnny was supposed to be annoying; that was his character, the annoying, hotshot punk kid.