Only top 5... hmmm....
Hunter x Hunter - It's just so well written. The characters are all memorable and likable, none of them are black or white. They're all the gray area which gives them a lot of depth and makes them feel very real in a sense. The arcs are all well paced and original--I mean in the Greed Island arc there was a dodge-ball match that was actually pretty exciting to watch. I love the main 4 and could just talk about them forever and I want them to always be happy,,, Natsume Yuujinchou - Such a nice series. Natsume's incredibly precious and deserves happiness more than most people I know. Nyanko-sensei's just nyanko-sensei and is funny on occasion. It made me cry at least twice and was very relaxing and it was one series of the few I can think of that non-anime fans might like. It's only been a year since I watched it but it's nonetheless kinda nostalgic for me, that's just the kind of atmosphere the show had. Haikyuu!! - This is what got me into sports anime. The characters are all likable and also memorable. All of them--every single of them is a giant nerd It's so great. It also helped that volleyball is one of the few sports I like and I have friends that play it too so I understood what was going on during the matches. And HQ has one of the few fandoms I really like so that's a plus. Daily Lives of High School Boys - I don't think any other anime has made me laugh as hard as many times as this one did. All the skits are just amazing. If this never gets a second season I'm gonna be so sad because 12 episodes just really wasn't enough. Code Geass - I like seeing the strategic side of battles. And I found Lelouch and his whole thought process interesting and different. I also just really like military anime so... I truthfully don't remember the main reasons why I liked this one as much as I did
Mawaru Penguindrum, Katekyo Hitman Reborn, and Oofuri get honorable mentions