Most Amiga games are just using 320x200 so on PAL displays you often get empty space on PAL Amigas. It is normal. Some games are designed to 320x256 display but they are quite rare. Best Amiga games were ports from other systems (ST/PC/C64) where 320x200 was standard or from the USA...
IIRC some later Amiga 500 models could boot to NTSC mode. Dunno if it would help.
In my opinion empty space is not problem because you get square pixels... stretched display looks awful.
