I never really liked the forth season. It was okay, but I didn't like the Royal Knights arc at all (it was soooo annoyingly pointless, they could have done everything in one arc). The third Digimon season was pretty cool, but didn't really feel like a digimon show once the late season hit. But my favorite seasons would have to be both Digimon Adventures. Second season was the best after the Digimon Emperor arc. 

I'm pretty hyped for the third Digimon adventure too.