The reason to keep your PS1 hooked up.
The whole platformer/rpg thing had already been done in the past. Namely Zelda II for the NES and Super Adventure Island II for the SNES... but Tomba is done so much better... and here's why: it's the funnest platformer I've ever played with its sequel as the only competition.
From what I gather, to make a great platformer (mind you, not an extremely successful one) you need some kind of ability to change the gameplay. Leave the "get through the levels as fast as you can with as much as you can" to the 16-bit era. To be a 3D generation platformer, the developers knew Tomba needed all the quirks of the past, but with a twist.
Tomba is about a little barbaric pink haired kid named, you guessed it, Tomba. He's lost some ring his grandfather gave him and he's gotta go find it... why? Well, who cares. As soon as you're thrown into this game, you're in love. The action is 2D but they've thrown in 3D elements that make it a little less linear. You're backtracking a lot of the way, which isn't usually as common.
The game is split up into tiny little missions, which you get AP for completing. Unlike most platformers the points actually count for something, once you get certain amounts you can open little boxes called AP boxes and get various helpful items. The missions can be completed whenever and some span the entire game, but by completing them all, there seems to be much more of a feel of accomplishment than rather having to run through levels getting "100%." Oh and you molest pigs. Sorta.
The sound is just about right, it doesn't get in the way as being too much, but is just right when it comes to your regular platformer tunes... I do find myself humming some of them sometimes.
These days I've searched out newer PS2 titles that even somewhat resemble the mechanics found within this game. I've tried games such as Veiwtiful Joe and Klonoa, which are still fun, but they just don't give me as great a feel as Tomba. It's a classic... or atleast it should be.
You can also find this game for around 15 - 20 dollars used on the internet... Good luck finding it in a used game store. This is not one they keep very long.
Anyway, this is as good as platforming gets. Anyone backtracking on the PSone (as I currently am) must eventually add this one and its sequel to their collection. Here's to Tomba 3! (I wish.)