They were all good except 5(worst thing to happen to Digimon ever)
And let's ignore the fact that Savers is considered the best season.
I've only seen Adventure through Tamers (seasons one through three, and with the exception of the first half of Adventure, all dubbed), and out of those Adventure was by far the best. Adventure 02 sucked due to the plot going all over the place and the lack of characterization (it didn't live anywhere close to its potential). Tamers had a lame Digital World (in my opinion) and became boring once Rika started being nice, but it offered a far more serious experience than the first two seasons (particularly at the end with the Takato and Jeri).
Season 2 was da best by miles (i only seen 1 and 2 and a bit of 5 cuz i iz english),but 2 just rocks, charaters,digimon it just rocks. why well there is 3 reasons >it rocks>it rocks.it rocks.whooooo season 2 rocks.