There's no truly successful online dating platform because online dating is a stupid idea. The user gap is physical presence. Every site is bound to have a niche audience, the few people who can get over the stupidity long enough to try out an interesting-sounding idea. Eventually they either realize it's stupid and stop or they get really lucky and meet a spouse.
If you want to start one, I say you should just pick the coolest sounding gimmick you can find and hope enough other people think it's cool too. Then you can extract some money from investors. Pray it lasts long enough to exit.