While I understand the comparison you seem to be trying to make, your 3d engine compared with the Unreal 3d engine (not the tools), I think this is a mistake. You need to clarify more since at first glance your engine is not comparable to the Unreal engine. Most developers are going to see a statement like that as a comparison of the Unreal development tools, which I don't see anything like that on your site. The big sale for Unreal with developers is with their tools and pipeline. Unless you can match that in some way I would change that statement. I can download the Unreal Develoment Kit for free and start making a basic 3d game out-of-the-box with the tools they provide without needing additional programming or artwork immediately; can you claim that? Is there a level editor of some sort, scripting IDE, events IDE, and so on?

Go to unrealengine.com and poke around. I don't see the comparison. Now, if you could provide some things along these lines, tool-wise, then you got something.

If you need a way to describe that your engine allows for the development of complex 3d games then I would suggest you use the statement "Our engine allows for the development of complex 3d games". Nothing more needs to be said and comparing your engine with a far more complete and potentially superior gaming engine/toolset is misleading and inappropriate.

I would also suggest you allow people to download the SDK and try sample games without having to sign up for anything.