There's no doubt about it that Cher, Madonna, Gaga, and Britney are all gay icons. But who is the ultimate? When you hear "gay icon" who immediately comes to mind? Who makes the most gay-friendly jams? Who does the most to promote equality?
What about Kylie Minogue? Cyndi Lauper? Gloria Gaynor?
Gaga/Madonna/Cher are definitely the trinity (of recent times). I'd say RIGHT NOW Gaga does the most, and Cher's music is the gayest , but Madonna is the jack of all trades too. I don't like ranking people in this though because all three have dedicated their careers to gay people and should be applauded.
It depends. If you're talking about the last ~3 years, it is EASILYYYY Gaga. Like any non-delusional will agree that she's been doing the most when it comes to gays.
In terms of lifetime achievements? Probably Cher & Cyndi. Kylie comes a close third.