Black box games and some other early games:
Therse are mostly unchanged from the NTSC version, and will therefore run 17% slower on a PAL NES, with 17% slower music and with a lower pitch. Therse games will run correctly in a modded NTSC console. At some time, the PAL version of Super Mario Bros was patched to run at slightly faster speed than the NTSC version, with slightly faster music at correct pitch. Examples: Ice climber, Wrecking crew, Kid Icarus.
Early Konami games:
Most of therse are just the same case as the Black box games, but many has been fixed to prevent glitches. Despite being patched compared to the original NTSC version, it will still play correctly on a modded NTSC console. Examples: Top Gun, Gradius.
Most games released after early 1987:
The speed of the music has been patched to run correctly. The gameplay is still slow, and the pitch of the music is still lower. Examples: Battletoads, Super Mario Bros. 3, Metroid (exception: intro music is of higher pitch than the NTSC version).
Some few games from Nintendo released after early 1987:
Music plays at correct tempo and eventually correct pitch, but the gameplay is slightly faster. Examples: Tetris, Nintendo world cup (in terms of running speed. The actual game-clock may have the 17% slowdown).
One oddball is Kirby's adventure. In the PAL version, the music is identical to the NTSC version, with correct pitch and tempo. The main game engine seems to run with the regulat 17% slowdown, but the odd thing is that Kirby still moves with the same speed as he does in the NTSC version (in other words, Kirby is faster relative to everything else).
Another oddball is Top Gun 2, which seems to run at exactly the same as the NTSC version, and it's therefore the ONLY correctly optimized NES game I have seen so far.
Edited by per, Tue May 4, 2010 7:45 AM.