By the mere fact that he took a relative 'weak, old, peasant nation (Tsardom)' and transformed it into a massive, modernized powerhouse that has had a major influence on the course of European, Middle-Eastern and Asian history for well over 350 years, I think he does deserve the title of being The Great. He established one of the greatest empire in world history. To his merits include: found Saint-Petersburg,defeat Sweden, which conclude Swedish efforts to conquer other lands. I sure but for Peter, Russia wouldn't have returned on Baltic shore.
Not saying that he was probably full of fallacies and the cause of many wrongful deaths, the legacy that his 40 year reign left behind is (at least to me) worthy of being called The Great.