They would still be really terrible. There are global resources (generally the ocean stuff) and there are continental resources (each continent has 4 (or 5?) unique resources). generally, it's nearly impossible to get 60% control of a global resource. You need, say, 14/20 turtles. But the continental stuff is where the monopolies come from and in extreme cases, you might have a small continent to yourself and get an easy 4 or 5 3/5, 4/5 type monopolies where no one else has any, but even with a couple other civs on a continent, it is not necessarily hard to get a couple 6/10 type monopolies where 2 of the other AIs have control of 1 or 2 instances. But on a standard map, a monopoly where 5 of 7 opponents don't have a copy is still a huge bonus.