Well, now that this thread has been revived, I might as well post a few more.
Castlevania 2's Dwelling of Doom (start at the beginning of the track)
...sounds like Yngwie Malmsteen's Far Beyond the Sun (see 0:23)
This melody from Top Gear on the SNES:
Sounds almost identical to Billy Joel's "The Stranger" (see 0:57)
The BGM from Jurassic Park NES's first stage
...was later used in Platypus on the PSP
Many of the original Doom's songs were inspired by rock and metal tracks. You can find a list of the similarities here:
http://doom.wikia.com/wiki/Doom_musicI'm not sure if this counts, but Lemmings incorporated a ton of public domain music into its soundtrack:
Forest Green/O Little Town of Bethlehem
How Much is that Doggie in the Window
London Bridge is Falling Down
Turkish March
The Can-Can
She'll be Coming 'Round the Mountain
and so on.
Although I think a lot of this can be attributed to the fact that musical possibilities are inevitably limited. When you consider the millions of artists across all genres and eras, many producing over a hundred works, there are bound to be similarities between random songs. Compare the end of The Beatles's "A Day in the Life" to the hook from Billie Joe Royal's "Hush" (later made famous by Deep Purple) for one example of an identical riff that was (supposedly) coincidental, not stolen.
The Castlevania fanbase often credits Michiru Yamane with remixing tunes in her soundtracks that, in my opinion, are not intended to be remixes - they're just a sign of her limited musical range. That's not meant to knock her as an artist; she's one of my favorites.