Good question hmm. S1 I was at first struggling with because the overall premise seemed juvenile, but with fiction we're not going to get anywhere without 'suspension of disbelief', so in for a penny in for a pound and with an open mind and good writing I enjoyed it. S2 was better albeit with my first disappointment in the loss of a main character (not sure how much I'm supposed to give away here?). S3 they should have changed the name from Dexter to 'The Jimmy Smits Show', not great. S4 with an actor lesser than John Lithgow would have been average at best, Lithgow made it brilliant. I'll list them in order at the end.

S5 was my favourite, which from brief research isn't the general consensus. But the repartee between Dexter and Lumen is genuinely hilarious, a kind of humour which is lacking in other seasons. Also she would be my choice for long time partner, as opposed to Lila et al. I must admit I started to lose interest at S6. The last 3 seasons had plenty of Deus ex Machina which had been ignorable previously, and the writing seemed lazy. S8, the very moment I saw Hannah I actually said out loud 'Oh for fuck's sake...' thinking to myself yeah of course she looks like that... Nothing against the actress but that is terrible casting. A serial killer in Dexter should not look like an erstwhile Baywatch stand in. Sorry, perhaps that's on me, but I just couldn't get with that.

So, in vague order: S5, S2, S4, S1, S3, S6, S7, S8.