Ah, really. I don't have any SEGA PAL games anymore.
Isn't there anything good about PAL games (besides nostalgia for some) often most expensive, crippled with 50hz/bars and crappy cases.
Most SMS games were not region dependent, and SMS was much more successful in Europe because Nintendo couldn't strongarm developers to not produce games for it there unlike in the US. A few PAL games that did too much processing in the overscan region or had otehr timing issues may have had artifacts, but for the majority of games, the PAL SMS games ran stock on NTSC hardware. Sonic infamously had a NTSC specific region sticker on the box.
Sega had lockouts with Megadrive/Genesis, but it was game optional. My PAL Psycho Pinball and Micro Machines II carts run fine on my US Genesis. Then the Turbografx never really made it out of US/Japan, so the relatively few test market PAL consoles are just NTSC hardware with gimped 50Hz video.
NES is in a similar situation with many games running on stock NES hardware with the region chip disabled, and in rare instances wher the PAL games were optimized, run too fast and at wrong pitch on NTSC hardware, or slow/flat on PAL hardware. SNES and N64 also had lockout chips and physical tabs as well, which can be broken on a US SNES to support Super Famicom carts but not the like-shaped PAL carts. Nintendo started adding microcode to most SNES games released after 1992 to prevent pass-through converters from playing out of region carts on PAL SNES systems.
Atari 2600 used incompatible color pallets between PAL and NTSC systems and the 50Hz refresh rates made most NTSC TVs roll or at least crop the bottom. 7800 was completely incompatible across regions.