In Rod Laver's book, he says the US Open is 2nd in prestige behind Wimbledon.
This is probably true (no matter how subjective) due to all the money the Americans pour into the US Open.
The French Open will always feel a little smaller, as it is less grandiose and doesn't have quite the same snob elitist factor of Wimbledon.
Wimbledon is the fixed #1, regardless of its organization or quality of tennis. People have simply decided that it's the best due to a romantic ideal of tennis on English lawns. It's supposed to be great - why, no one knows, but we just have to believe it as everyone else does. Whatever floats their boat.
From a fan's perspective:
1. French Open .. historically produces the greatest stories and most heroic feats .. the atmosphere frankly is electric and frankly I really like modern clay court tennis (okay, rewind about 5-7 years and you have the real goodness).
2. Australian Open .. most comfort for your buck .. beautiful city; well organized event.
3. Wimbledon .. big step down .. expensive; too much rain .. tennis not in any way objectively better than the other four majors .. in fact, probably worse.
4. US Open .. great tennis, but it's a giant walking advertisement and a church in one .. they'll tell you how much they love God and sell you useless shlt you don't want .. not unenjoyable until the aftertaste sets in.