Audition might be fun to try. The community on Redbana sucks though, from my experience (I've played it for years). The standard mode also doesn't have much to offer in the way of rhythm.
You can also try:
Stepmania
FFR (like stepmania, but browser-based)
o2mania (offline version of o2jam, unless you can find a server to play on)
Guitar Hero
Rockband (playing the keytar or drums is always fun)
FOF (free PC rendition of Guitar Hero with custom songs fretted by community members)
DDR (great fun and also a great work out)
Rocksmith (if you're actually into playing music as well as playing games)
osu! (seriously, try every game mode if you haven't already, you might find one you really like)
