Apart from Burton, which snowboard manufacturing companys are considered in the top 3

well alot depends on the type of riding too.
and if u mean top by top selling ide say burton then ride then forum.
but there are alot of things you should look into also
1 price range
2 conditions your riding (like park or powder?)
3 size of boards
ect.
if your looking at park boards look into capita, rome, technine, and step child

Do not assume that Burton is the best at everything - it isn't. It just has a name that is known and hyped more than the other brands.

For Freestyle / Jib: Rome, K2, Gnu, LibTech (Burton is not in the list).

For All-Mountain / Freeride: Ride, K2, Nitro (maybe Burton would be 3rd on the list)

Good Luck