Mafia: Definitive Edition is more than a spit and polish of the original 2002 game: it's a thorough remake, which is lucky because the original definitely looks like an open world game from 2002. We've not seen much of the game in action so far, but now, embedded above, there's a substantial 15 minute gameplay video.
The video comes courtesy of IGN, and aside from the footage, there's not much in the way of new information. Some features are reiterated, such as the completely redesigned "period authentic" vehicles. There are bikes too, which as far as I know weren't in the original.
The 'Trip to the Country' mission dominates most of the video. If you're curious about how it looked back in 2002, here's a let's play of the original. If you like what you see, the game releases on September 25.