Season 1 - Solid and entertainig overall, but definitely not a classic Star Trek season by any means. Tends to veer between good and average a great deal more than I would have liked. I totally understand why many would find it a bit "meh".
Season 2 - No change here. For me, pretty much on a par with S1 - see above. Feels a bit like complacency has set in on the producers/writer's parts - with no attempt made to spice things up. Very much playing it safe.
Season 3 - A definite improvement on what's come before, actually, pretty damn good. Shows a willingness to shake things up and embrace new ideas.
Season 4 - This is more like it, an excellent prequel to TOS, and a golden season of Trek for me. If only they'd come out of the gate like this.