EDIT: Damnit, xhonzi! I was typing, kay?!
Don't get me wrong, I love the Paper Mario series as well.
Let me break it down for you, mkay? In certain ways, it's hard to compare the two, as all of the Mario RPG series takes things in different directions. As far as the action command aspects, yeah, the Paper Mario series takes that aspect from the original RPG and runs with in ways the original never dreamed. Each character has a specific function on and off the battlefield.
In terms of being an RPG, though, the Paper Mario series is definitely the most simplistic and stripped down of the bunch, though. The original game definitely has the edge in terms of story and characters, though, where your party members actually feel like characters and not just tools to use in specific situations.
The first game definitely has my favorite depiction of the Mario universe ever. I remember even attempting a novelization of the game when I was about to finish middle school. Sadly, I never finished it. Maybe someday...