Ah yes!  The (somewhat) eternal argument!  Is UFC better than WWE?  And is WWE better than TNA?  I will answer these questions:

Characters/Performers: UFC

This is almost a one-sided argument.  The UFC takes it because they do not use scripts for their characters.  In WWE and TNA, the character are created through written dialogue, so they are almost disqualified right there.  Also, the UFC stars, when in interviews seem more realistic when compared to the WWE/TNA stars who try to act in character all the time 

Matches: UFC or TNA

Once again, UFC wins due to realness.  The matches are shorter than some of the wrestling matches we see tohe bday, but the energy in the matches makes watching a UFC match better than watching a WWE or TNA match.  However, TNA is doing new innovations in their matches, which puts them above WWE. All WWE is doing is recycling their old matches and giving them new names.

Stories/Rivalries: UFC

OK, UFC wins this one not only because they are real.  They win this because you never know what to expect from their rivalries. For instance, nobody expected Matt Serra to beat, let alone KO, Georges St. Pierre a few months back.  Also, Gabriel Gonzaga was considered the underdog against Mirko Cro Cop at UFC 70.  However, he knocked him out with a vicious kick to the head in the 1st Round. In WWE or TNA, you can most of the time tell who is going to win what match and when.  For instance, who didn't think John Cena was going to beat Umaga at the Royal Rumble? And who wouldn't think that Samoa Joe was going to lose his 1st match against Kurt Angle, then beat him during their 2nd Match? Not to take anything away from them, but their predictability is very bothersome, especially for anyone who saw Smackdown last Friday.  After the beating the Undertaker took, I figured Edge would come out a steal the title from him, since in the script, Edge is an opportunist when it comes to the MitB Title.

Overall: UFC

UFC easily takes this.  Due to the realism of the matches and the people, they seem to perform better and be more enthusiastic about their job then the TNA and WWE stars. Overall, if all 3 were on at the same time, I would watch UFC and occasionally flip back and forth with TNA.