I think this was in the special features on the DVDs, but back in the beginning the PTB weren't sure who Sisko was at his core (Kirk was the adventurer, Picard the diplomat). It was at the start of S3 they realised he was a 'builder', since then he goes from strength to strength.
S1 and 2 do have a few stinkers in them (episode wise), but then again what series doesn't? But the worst early-DS9 has to offer still beats early-ENT and late-VOY. As been said before though, the storylines are consistant and build the characters up bit-by-bit, as well as introducing little titbits for future eps.
Even if you don't warm up to Sisko, there are still loads of great main and secondary characters to enjoy, with lots of good dynamics and evolution (Dax is a good example of this, going from being a bit rigid to becoming more relaxed as she gets used to being Joined).