Mafia 1 vs Mafia 2
Which experience trumps the other? Obviously the mechanics/graphics in Mafia 2 are better since it's a new game, but I'm talking about the overall experience from beginning to end.
In my opinion, whether it's nostalgia or not, Mafia 1 is slightly better. Tommy was just a much more likeable protagonist than Vito. It also helped that Tommy was just a taxi driver, hence it gave the player the immersion aspect of being a rookie in the mob/killing business. Vito was already a war veteran and his decisions throughout Mafia 2 are questionable at best. He has no trouble killing people (like Tommy did) and even gets involved in the drug game.
As far as other characters are concerned, I think Mafia 1 has an edge there too. While Mafia 2 had one really interesting mentor character (Leo Galante) I thought that Mafia 1's roster was quite engrossing all around. Paulie and Sam's relationship was much more personal than Joe's and Henry's. You really felt for Paulie when he died at the hands of Sam, because Paulie was gut shot at the gas station and waited for you to rescue Sam rather than go to the hospital immediately. Because of that, Sam was a much more appropriate villain than Henry and his informant status.
And when you compare them storywise, Tommy ends up in a much different place at the end of Mafia 1 than Vito does at the end of Mafia 2. Tommy turns from a taxi driver to a mafioso to a disgruntled one looking for redemption. Vito is simply looking to profit all the time and doesn't change all that much other than learning that prison is not a good place to be and that the mafia doesn't forgive (although how he didn't figure out that by the end when they take Joe away is beyond me).