Of the four, Season 1 has the most episodes I'd rather not rewatch. And they usually come in bunches. "Unexpected" and "Terra Nova" back to back, really early on, is kind of a buzzkill. "Rogue Planet"/"Acquisition"/"Oasis" is possibly worse, though I do always appreciate seeing Odo again. The rest of the season is pretty good to decent. Definitely a better first season than TNG or Voyager had.
Season 2 only has two episodes I can't really stand, "A Night in Sickbay" and "Precious Cargo" but they are easily worse than anything in season 1. "A Night in Sickbay" is worse than most things in general. The season on the whole lacks direction but episode to episode there's little that really turns me off, other than the previously mentioned clunkers. I used to be pretty down on this season and the series in general but these days I tend not to put any one season entirely in the minus column. There's honestly worse in the franchise.
Season 3 has some good stuff in it but I don't know that I'm sold on it as some massive improvement over the first two seasons. Season 4 on the other hand does stand out as the best of the bunch.