The right one is the one God approves of. It comes down to the fact that the right person is the the person God approves of - in whatever religion He is. The question must then be "what does God approve of". Islam and Judaism have very detailed laws that are supposed to show this - but laws become relative and even obsolete as time goes by, as culture and society adapts. Unless they point to a way of life that God intends to do something with. I say "do something with", because logically there is no way that whatever we do can be "sufficient" unless it satisfies God's purpose for it.
In the first place, for God to be your God, He has to reveal himself to you. Otherwise you wouldn't matter to Him, and it wouldn't matter if He was God or not. The next question is how He did that. "Did", because He would have made himself known "to you" from the beginning of creation - whenever "you" were born, it would have been possible to know Him. It would be a "religion" that has existed since the a relationship with God was humanly possible, in whatever form. And it would still an be equally valid way of knowing God today - despite scientific advancement or spiritual depravity, despite anything life can throw at you.
In the second place, how did you lose touch with Him? What went wrong? That's what seeking God means. Everybody's seeking Him - and there are as many "religions" as there are personalities because everybody looks for God in their own way - and quite often also on their own terms. Some stop looking altogether. We would expect God to restore that relationship somehow, because if He didn't it would mean He has rejected us. And if He only let himself be found by our efforts, it means our abilities are more important to Him than a possible relationship with Him.
But if a personal relationship is what He desires, it somehow means something to Him - the only reason for that can be love. And if He loves you, it would be despite of your lack of understanding, or abilities, or holiness, despite everything, except of course rejecting His love. He can't force you to love Him. But if loving Him is even possible, it must be humanly possible.
Let me get to the point. The only reason to belong to a religion is if it enables life with God, while loving those just as lost and human as you.