Uh, so they are PCE games ? Paste a sample of the CUE. There's just not enough info on what's going on here. Did you check the CD-R burn with an emulator ?
The ISO file ranges 100-600 MB ? If so, it's a BIN file with an ISO extension. The extensions can be interchangeable. I mean, you can rename it to whatever you want, .IMG, but .BIN is usually the most popular choice for general mixed-mode CD layouts. CloneCD always uses .IMG for its full CD images, you get the idea.