This is one of those "alternative history" scenarios where you don't have to look too far since Hillary DID win the popular vote with 65,853,516 (48.5% votes) to Trump's 62,984,825 (46.4% votes), but lost in the electoral college by receiving 232 (43.1%) of the electoral votes to Trump's 306 (56.8%) votes.
That makes this question a bit like the "what if the British won the War of Independence?" Where one should just look at Canadian History.
Anyway, Hillary Clinton would have won the election if the electoral college didn't exist, but she would have been stuck with a legislative branch that was controlled by the opposite party. Not to mention a party which dislikes her intensely (as do quite a few democrats).
I would guess that we would have another ineffective Clinton administration that would probably last only one term.
But, don't get your hopes up about it being much better than the situation the US is currently in since the legislature would have been the same as it is now.