Over the last few weeks I've been helping the guys over at Randomised Gaming having a look at this issue, now that we have a NTSC Sega Mega Drive. We've found quite a few titles that have had some form of optimisation and here is what we have found so far: Word of warning the video is over an hour long the first 20 or so minutes covers the differences between PAL and NTSC, which you guys here don't need to watch. There's a break down of the video in the video description. Hopefully it will help a few people out who have NTSC machines and don't know which PAL games to buy. There's some really funky affects that happen with some games. We are also looking to try and create a complete list of all PAL optimised games, as currently there's a lot of mixed information all over the net about the subject and no one seems to have stored it all in one place.
Two games I know that have 50Hz optimized versions: Thunder Force 4, Rocket knight Adventures And those 50Hz versions will only run on 50Hz consoles <period>. Edit: I actually tried to remove region restriction on these two but they glitched so bad on 60Hz I just left them alone...