You can buy a product commonly known as floor leveler. Mixed right it
will do just what your asking, fill in all the valleys up to the
highest point provided the highest point isn't more than 3/4". Get
yourself a set of knee pads and a finishing trowel and do small areas
at a time. Home Depot selles it, I don't know about lowes since I've
only been in 2 of them and found they have the dumbest employees.
You can also hire a concrete company to do this but I'm going to guess
that how the floor ended up the way it did. You can go the epoxy way
but I'll bet you spend almost as much on that as the floor itself.
Lou