Finaly watched the last 4 episodes, loved when Van Alden finaly snaped and beat Al Capone up, got realy shocked at when he was killed, even though it was so obvious. I remember seeing some people around here discussing the possibility of a Lucciano/ Capone spin-off, right before the final season started, i myself would love to see that happen, could cover many of the things that happened between seasons 4 and 5 but weren't explored, and would be a sort of "rebrand" to the show, pretty much bringing old fans back, but also being advertised as something new viewers can easily get into.
Probably will need to rewatch the whole show, but right now i rank the Seasons as being: 2 > 3 > 5 > 1 > 4
I barely remember Seasons 1 and 4, they also had the most forgetable main villains for me, Season 3 was a great ride, but i think 2 was better put together.