Factors I tend to look for in RTS
Base building / resource acquisition (as opposed to capture points / ground control, though they can be used in tandem).
A decent technology tree with new and/or upgraded units available depending on the structures so far built.
Variation in unit types/capabilities.
Balanced units/structures for opposing factions. They don't have to be the same at every level, but the overall potential of each faction should be comparable.
