Ma long doesnt have really "good" serves for that high level. I think chen Qi, ma lin and zhang jike probably have the best serves.
I think ma long's serves are with no spin or just a little side backspin but just about enough to make you hit the net if you dont read the serve well.
You should check the match ma long vs wang hao. Ma long did a serve and wang hao just pushed the serve over the table and not just by a little but alot. Maybe you can copy that serve.
But if you watch the ones I mentioned above, they got so much spin on their serves.
And of course xu xin has a decent serve aswell, but he hides it.