NO route across Montana is interesting. You have a choice between boring, with some facilities enroute (Interstate 90) or extremely boring, with almost no facilities (Hwy 2, the "High Line").
It's endless desolate country punctuated by the occasional grain silo. The only advantage in taking Hwy 2 is that if your destination is Glacier Park, it deposits you right at the east entrance, whereas you're still three hours away via US 89 if you take the I-90 approach. Either way, it is country best sped through as quickly as possible. BTW, in Browning, the Museum of the American Indian is definitely worth a stop.