Yes, Napoleon could have won the battle of Waterloo. Actualy, despicte all the inconveniences, I think that tha battle was still his to win, if Blücher hadn´t arrive at that point. I once read that it wasn't Wellington that won the battle, but Blücher. I guess that´s a bit of exageration, but I do think that Wellington's role in this battle is overrated, as the battle itself is.
The important thing is that even if he had won, he was probably doomed anyway. There were still the other armies of the coalition to face, and they were coming. Maybe history would have registed the name of some other small french, german or belgian village, but I woldn't bet on France in 1815.
Maybe for Napoleon the fate would be different. If he was captured by a different army, he could have been sentenced to death. This way he ended up in St. Helena, which wasn't exactly very nice either. What is curious is that there was some strong arguing in London newspapers at the time about what to do with Napoleon, and there was a strong party that favoured is release, and that ststed there wasn't any british law that could convict him. I guess this tells how big was his fame and reputation for even gathering so favourable reactions in one of his major enemies.
BTW, thanks Napoleon (the poster) for making a thread not realated to WWII.