I agree, Lammy is better than Parappa, but I'm still hunting (not as much though) for a copy of Parappa. You don't necessarily have to freestyle to win, I just followed the commands.
There is so much more to do: Beat the game, then beat it with Parappa, beat the versus stages, etc. It's a lot harder too. I haven't even gotten Cool mode on all the levels, and for Parappa, there is a specific formula, so on that I beat every level on Cool.
All in all, it's a great deal, better than Parappa and definitely better than Parappa 2 which was just a piece of crap. I liked the songs in Parappa 1 better, but the guitar just sounds better to riff on.
It's sort of funny though, I got this game for $15 in '99, and it's $10 almost 5 years later. Good to see it's still around though.