All you people who think bettas are "boring", etc are obviously keeping them wrong. If you have the room try sticking 1 male and a few females in a larger tank with a few peaceful fish and watch, you'll be pleasantly suprised.
Overrated: Defanantly discus, goldfish to a degree (common and I wouldn't keep just goldfish), cories, a few others I can't think of offa the top of my head.
Underrated: Defanantly Oddballs, especially peacock eels (I know I rave about them at every possible chance I get, but ask anybody who's kept them, it's justified), alot of the rarer cichlids I.E: Lamprologus, Neolamprologus, Aulonocara hansbaenschi, Apple snails (Seriously, these guys have a ton of personality, mine love sliding over the air bubbles and taking off, floating half-way round the tank before plummeting to the floor), Upside down catfish, lots of others.