While Unity has features that the BGE doesn’t have, that reason alone is not going to make your game commercial quality.
While some engines today make it easy enough to create gorgeous backgrounds and shaders, all that eye-candy is not going to help if you’re not skilled at making the assets using the shaders or if the logic that makes it a game and not a walkthrough or just something to look at is poorly done. Unity though, as I’ve heard, can make use of ready-to-use logic ‘components’ where you can just bolt them together and get some basic gameplay out of that and I think has a UI creator as well. The natural disadvantage to that in a popular engine is, and I’ve played enough Unity browser games on Kongregate to say this, a lot of games end up having the exact same walking system and UI button style, so you still would have to make your own system if your game is ever going to stand out.
Unity having advantages doesn’t mean that the BGE doesn’t have any, the BGE offers several features only available with a commercial Unity license and you can’t make the asset pipeline any shorter than where you make the game in the same program you model them in, it may not have any clear speed advantages, but the Python API allows multiple ways to greatly increase the speed of your logic with hundreds or even thousands of objects.