Outside of handheld systems, you don't see many commercial 2D platform games anymore. But every so often, we're fortunate to get one of excellent quality that actually takes advantage of the capabilities of modern consoles, such as Konami's Castlevania: Symphony of the Night and Namco's Klonoa: Door to Phantomile. Released in 1998 for the Sony Playstation, Klonoa didn't get a lot of attention. Because of this, it is now expensive and hard to find.
My friend Phil introduced me to Klonoa, and later sold me his copy along with the PS2 sequel, Klonoa 2: Lunatea's Veil. (This one is not so rare, and although I don't think the music and characters measure up to the first game, it is otherwise a worthy sequel and I do recommend it.)
I won't attempt any kind of thorough review of Klonoa on this page. You can find plenty of those on GameFAQs and elsewhere.