The best (and hardest) way would be to somehow extract all the data of the stages and create a custom rendering program that would display the levels straight on, with no perspective at all. A pipe dream really; coders capable of such feats are very rare and such work takes time even for them.
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Current projects: Ristar-The Shooting Star (Gen), Sonic The Hedgehog (Gen), Sonic CD (Sega CD), Mega Man Zero (GBA), Battletoads (NES), Bucky O'Hare (NES)