Not so. Great Person cost scales linearly in this game while it was exponential (iirc) in Civ4. That is, if the first one costs 100 and you produce 10gpp you get it in 10 turns. The second one costs 200 which you get in 20 turns, the third one costs 400 which you get in 40 turns. With philosophical you got the first in 5 turns, the second in 10, the third in 20 because you added twice as many points.
However, in civ 5, the first costs 100, the second 200, the third 300, and so on. So again assuming 10 points you get the first in 10 turns, 20 turns, 30 turns, etc. while the Babylonians (correct me if I'm wrong because I don't own them) halve the cost of this, putting them at 50, 100, 150, etc. or 5 turns, 10 turns, 15 turns and so on. So the effect is much better than just getting the first one a bit earlier.
Well it doesn't exactly halve the cost. It's a +100% bonus, so with other bonuses like the garden or national epic the Babylonian bonus is less noticable.
And the cost increase for the first 10 great people was exactly the same in Civ 4- 100, 200, 300, etc. It didn't increase until after 10, when it went from 1000 to 1200 points.
Obviously you do get more great scientists with the Babylonians. It's just that you don't get twice as many, like some people think.