I think my favourite would be Miss Kobayashi's Dragon Maid for how positive, funny and happy it is. Though in contrast, Serial Experiments Lain is mindblowing, it's seriously just wow. Death Note and Naruto are both reallly solid too. Date-A-Live is great, Another is really amazing. Hard to pick a favourite when so many are so good for different reasons xD
For me, it's kind of difficult to pin down what my favorite anime of all time is, since it tends to shift a lot depending on my mood, but one that impacted me a lot the last couple of years is a more obscure series called Kokoro Connect, if anybody's familiar with that.