That's... Not exactly right. A wholly proportional system would actually make the big state/small state issue worse.
States with fewer electoral votes will present a harder path for candidates to improve their standing. In an extreme example, a state with only three ev's will essentially always give two to one candidate and one to the other, the winner being first past the post.
States with more electoral votes will also be easier to focus on to run up the score. Right now winning California gets you everything, in a proportional system more votes in Cali gets you more EV's than more votes elsewhere.
All it would do is even out the campaigning between large states and give a more perverse incentive to ignore the small ones.