Best themes:
Any version of Pyramid (not including 2002)
The Price Is Right (obviously)
The Match Game/Hollywood Squares Hour
Russian Roulette (game shows and rock music do mix!)
Press Your Luck
1 vs. 100 (the melody gets stuck in my head)
Honorable mentions: The Moment of Truth (the show sucked, but the music is really good), Blockbusters (1980), Family Feud (1999) (that will be controversial), Hollywood Squares (both songs from 1998-2004), Think Fast, Double Dare, really any show whose theme was composed by Edd Kalehoff
Worst themes:
Any original show currently airing on GSN (I don’t care for that synthesized generic crap)
Chain Reaction (2006) (the song is fine, the lyrics are horrid)
Jeopardy! (1984-1997) (another unpopular opinion, I liked the newer versions)
Pyramid (2002) (see GSN for reasoning)
Monopoly (again, most songs don’t need lyrics)