Yeah, I agree, the pilot was universally panned by viewers and critics alike - so much so that when the pilot went to series, the network had so little faith in it that the first season only had five episodes.
To me, the earlier seasons (which were mostly shorter) show signs of how much it struggled, and the episodes tend to be a tad slow-paced, dull, and feel like drawn-out stage plays. I'm with Mo, only for my personal opinion, I'd say anything from Season 5 though 9 instead of 3 through 9: I feel like 5 is when the show finally found its footing, structure, and solidity.
Now, many critics say the last two seasons (8 and 9) are awful, because by then, the show's co-creator/showrunner had left, and they feel the writers went way too far in making situations absurd, far-fetched, and unrealistic . . . but in my personal opinion, they're two of my favorite seasons, but it's all up to you.
If you have TBS, they air four back-to-back episodes early in the evening (6:00 - 8:00 EST) every weeknight except Monday (which they devote to a marathon of Seth MacFarlane shows), and they happen to be in the middle of Season 8 right now, so there's a good place for you to start. Bear in mind, though: TBS has a tendancy to really bounce around the seasons a lot, so just because they're showing Season 8 right now doesn't mean 9 will follow afterwards.