This page wasn't supposed to be comprehensive or anything, but I was looking hard for lyrics to the Japanese Pocket Monsters songs. I couldn't find any on one page, so here's where you can find some of the songs...|
To actually download the songs, I recommend the multimedia section of Pokémon Invasion.
Team Rocket's Glorious Hole in the Wall has "Lucky Lucky"
Kojiro-kun's Kawaii Pocket Monsters Sound Shack has the Japanese theme song (Mezase Pokemon Master) and first ending theme (Hyaku go Juiichi)
The Great Rocket Gang's Homepage has Rocket Dan yo Eien ni
The Cleft of Dimension's Pokemon Shrine has lyrics to the full-length Mezase Pokemon Master (under 'Japanese series)
With Love, Pikachu has Mezase Pokemon Master's translation
Woah! Pokémon Lunchbox, it has lots of lyrics and their translations. Opening and ending themes, Team Rocket songs... fabulous.
Another fabulous lyrics site! PokeLyrics has heaps of 'em.
Okay! I have lyrics for the 2.B.A Master soundtrack, the movie soundtrack and the themes; Pokemon theme songs and both Pokeraps.