John Deere would probably be your easiest to maintain as far as finding parts. But any of the original Cubs, Wheel Horse, Case-Ingersoll tractors, John Deere, even Snapper from 1980's on back seemed built pretty solid in size range you need for 2 acres.
Personally I would probably look for either a Kohler or second choice a Briggs engine as for most parts available yet. Onan would probably be the most difficult and most expensive to keep going. Although there are still some dealers around that carry parts for them. Tecumseh could be a little iffy now too regarding what will remain available. Just my 2 cents and not a penny more worth.