I assume you are talking about "one day" specialists and not test matchs. Until Kohli proves himself on pitches that aren't flat (England etc) then he is a very poor man's Gavaskar/Dravid/Tendulkar.. Of course he is exciting to watch on flat pitches but so is Warner,Roy, Guptill, etc, etc.
De Villiers is a better all round batsman/cricketer than Kohli.
I'm confused here. ODIs are mostly played on flat pitches. Either way 7000 runs at 51 with 25 centuries is s mighty fine effort.
Also I didn't say Kohli was superior to de Villiers. I said those two are the benchmark in ODI cricket. Aside from those two only Amla and Dhoni had ODI averages north of 50. Elite group I'd say
And final point Kohli has scored hundreds in Tests everywhere excluding England. So I doubt all pitches around the world are 'flat'