Bought Soleil not a long ago, entered the code via Game Genie, played a lot and...after all that discovered what it doesn't save. Read this thing about Sega's decision about RPGs with Game Genie on Wikipedia. There's any possibilities to launch european region-locked RPGs with ability to save? Found info what Mega Key 1 doesn't launch PAL games on US machine, Mega Key 2 too (though it will on Japanese one?).
I have the same problem with Soleil. I think the only fix is a region switch, so you can go to PAL on startup and then back to NTSC/US once it's passed the region check. At least it's supposedly worth it, since (a) the PAL/UK version has a better English translation than the NTSC/US release, (b) it wasn't optimized for 50Hz (I don't think?), so it does play at the proper speed at 60Hz, and (c) it's a heck of a lot cheaper than Crusader of Centy, and has a real clamshell instead of cardboard. What other PAL releases are region-locked and have a savegame function? Are there any exclusives or superior versions, as with Soleil? There's a list here but I didn't spot any others.
I thought about switch. I can't make it for myself since I haven't any stuff for soldering and it's not mine field. Yes, Soleil runs greatly on 60hz since it's not optimized and I don't know why some people telling what game runs very fast in NTSC mode. http://www.gamefaqs.com/genesis/916377-genesis/faqs/60595 - list of region-locked games. I don't know about superior versions. But just for example, Sega of Europe used the Japanese cover for European release of Light Crusader, it's great. Read that Super Key will boot any things on Genesis... Still not pretty sure about Mega Keys - also found info what they will play PAL-locked games on Genesis TOO! I don't know where's the truth. Internets are full of misinformation.
I just got a soldering iron for Christmas and am looking forward to adding a region switch to my Model 1. That said, a lot of the guides seem to be for NTSC/US vs. NTSC/JP, rather than a 3-way switch that includes PAL. Ha, I actually posted the same link! -- mouse over the word "here" in my previous post. That's one of the dangers of AG's "hidden link" formatting.