Gen 5 is a pretty bad generation for stall as far as I know, lots of powerful breakers running around.
Good generations for stall include: Gen 2, Gen 3, Gen 4
Decent/Mediocre stall gens include: Gen 6, Gen 7, Gen 5, Gen 8
This list is only counting hardcore stall as actual stall and not including semi-stall and bulky balance stuff.
It's hard to decide definitively which is the best for stall, but I'd probably say DPP or GSC.