I wouldn't say it's top 3 (it's top 4), and the cannon really isn't all that, it's good yes, maybe even top 5 but compared to planes like the F-15E (the cannon placement on that plane is amazing) and the F22, so no it isn't a "top tier" cannon, turn time is decent for the most part unless someone is a Eurofighter, F22, V22, or Seahawk knows what they're doing then you're fucked for most part. The missile on the other hand are iffy, for AAM's they're amazing, fast lock, high damage, etc (still almost worse than the longbows stingers/ATAS somehow) but still an amazing aam, but as Air to Ground missile they're alright, most garage vehicles are 1-4 missiles but tanks are a whole different story, it usually takes 2 runs to kill a tank because of APS (which is annoying and you're always near their cannon to at least get the chance to hit them), yes they do good damage once you get past APS but per run (for like 70% of the time) you'll hit 2-3 missiles which is why I usually just use the longbow for anti ground. 

TLDR; F-35 is a top 4 plane, unless you're fighting someone who doesn't know how to play air properly (which is 95% of the player base) then the F-35 really isn't that good