I have lots of rhythm games in Japanese...I read Katakana pretty quickly so I can easily figure things out when there's not too much text.
RPGs though, that's a little different. I have Mother 2 and I played it through, but I've played Earthbound so many times I knew what was being said. I've got the first Shin Megami game for the Super Famicom, but I got it fairly cheap in a stack of import games.
Old games, I can read the Japanese OK because the graphics wouldn't allow the more complicated Kanji to be displayed so a lot of it was written phonetically. Anything CD based or higher however, and I'm sorta taking a crap shoot on how much I'll get out of it.