You might be able to beat crops in that way if you dispensed with photosynthesis and crops altogether and came up with a completely different way to convert solar energy to carbohydrates. Somebody else in this thread said that a wheat field converts 1% of its solar energy to food calories. They didn't cite that and I don't have time to look it up, but if it's true it should be beatable.
Evolution can be stuck in local maxima determined by some path it went down a long time ago. If life happened to evolve an inherently inefficient metabolism, it would be stuck with it forever because you can't really go back on something that fundamental (we share glycolysis mechanism with bacteria).
And, even if evolution automatically did win, plants did not evolve to feed us. They evolved to reproduce themselves, and we have incidentally hijacked them to use as food sources.
Evoltution is great at tweaking, and would be hard to beat, but it might be possible to build something completely different. It would also be hard to tweak a bird's wings, but we have built aircraft with completely different designs that fly many times faster than any bird.
