Here are a list of PC games (some free downloads/online flashes) of games that plays like the Guitar Hero games.

Flash Hero [Online Flash game]
Freetar Hero
Guitar Zero
Frets on Fire
Frets on Fire X (FoFiX)
Rock Hero [Flash-based]
Rock Hero 2 [Flash-based]
Phase Shift
Guitar Hero PC Edition

Phase Shift is my favorite since it uses just about every in-game element from both Guitar Hero and Rock Band franchise.