I watched the show first when it aired and I was a teen. I was pretty much obsessed back then. I also read and own the books.
Currently rewatched and I had a lot of fun with it. My opinions haven't much changed over the years except that I don't find Bill as annoying and ugly as I used to as a teen lol. Stephen is not an ugly man after all.
[SPOILERS AHEAD]
I still think they should have used Bill more as a background character after season 3 but he especially should have never been a romantic option for Sookie again after season 3 either. It felt way too forced and probably only done because the actors are a real life couple. Bad decision. Sookie in the books didn't even think twice about him after breaking up.
I'm still a big Eric and Sookie shipper but I would have been ok with them not being endgame if the show would have at least given them a fair chance. What they did with them after s4 was just disappointing.
There was no need at all to kill off Alcide and Tara. Awful decision. Also Alcide would have been a fine endgame for Sookie instead of some random guy. The ship was a bit boring for me to actual root for them but they were ok and would have made sense.
The Hoyt and Jessica ending felt just as bad as what they tried to force with Bill and Sookie. Made no sense anymore after everything that happened.
Hated what they did with Terry's character and how he died. No need for that at all. They should have just kept him as a background character instead.
Also hated the fae storyline a lot. They should have gone with some storylines from the books instead.
Anyway that's all I can think of for now.
My top 5 characters: Eric, Lafayette, Jessica, Sookie and Tara (probably unpopular bc this subreddit seems to hate them). Also honorable mention to Pam.