RPGMemes

If you want the best rules to base a videogame on, I'd probably recommend you look at 4th edition.

4th edition rules are, largely, designed around running a systematic, balanced, combat simulation - most of the rules are deterministic and leave little ambiguity, or room for interpretation.

Most other editions of DnD have... more freeform rules, in places they read as guidelines for running a game, or they are ambiguous, or leave it up to the DM to decide how to run that particular thing. They're more conducive to roleplay but much less useful if you're trying to adapt them for a computer to run.