Such a poignant and important question to ask.. why Jesus, and no one else? The simple most concise answer would be that there is no one else BUT Jesus who can do what He has done, or say what He has spoken or be who He is.. God in the flesh.
Jesus is more than just a mere man, he is God incarnate; He is both fully God and fully man at the same time. He was prophesied of old, then centuries later fulfilled those prophecies via His Virgin Birth, His life, His death, His burial and His resurrection. The scientific numerical odds if the fulfilled prophecies was just by chance, would be astronomical.
What makes Jesus so different than any other religious figure/leader is that while other leaders may claim to speak on God's behalf, or declare a preset of appeasement rules, doctrines, teachings, principles, which is a system that one must achieve and maintain, or suggest in some way that all we have to do is look within ourselves to connect to God our Father and reach a state of nirvana; Jesus, according to His Word came to mankind, dwelt among mankind with the ultimate purpose to die and save mankind. All we have to do is believe and receive Him as Saviour and Lord. The scripture declares in (Luke 19: 10), "for the Son of Man has come to seek and to save that which was lost." There is no system of laws or pillars of appeasement that mankind could ever do, because no amount of "works" could ever save a sinful soul. So Jesus who is God in the flesh, did all the work for us so that He can re-establish the relationship and connection mankind had with God our Father. Jesus is our mediator between man and God because His sacrifice is the only thing that was accepted and received by God our Father, for the atonement of sins and redemption of man. The gulf that exists between mankind and God because of sin, has been bridged and by the cross of Jesus. It's because of His death, burial and resurrection we can now have a full and right relationship with God.
Another factor that makes Jesus different than any other religious leader is that Jesus is alive and His tomb is empty! All the other major religious figureheads, there bones are still in their respective graves awaiting judgement. The scripture declares, "for all have sinned and fall short of the glory of God" (Romans 3: 23); what is astounding is the thought that many in this world are following the teachings, rituals or principles of dead religious figureheads who themselves are in need of the Saviour for the remission of their sins. Furthermore in (Matthew 28:6), the scripture reminds us of this truth: "He is not here; for He has risen, as He said. Come, see the place where he lay." The body of Jesus has never been found, nor has it gone missing because He's alive and well and is currently working on our behalf, interceding for us at the right hand of the Father, as well as preparing to return for the ones who have said 'yes' to His call of salvation. When He returns (which will be sooner than we think), He will eventually reign and rule on the earth and we will have the privilege to reign and rule with Him.