PAL games used a different lockout chip inside to US and Japanese carts. You'll need a region converter cartridge or Action Replay such as this to test them firstly. After that, there may still be problems; many PAL games later on were optimised for the greater number of display lines that are displayed, and sped up to compensate for the 17% slower refresh rate.
I've tried Super Tennis PAL on my US SNES and it goes at a hyper rate! Definitely an amusing and "fun" challenge playing that![]()