Jesus says, "I am the way, and the truth, and the life. No one comes to the Father, except through Me." John 14:6 (ESV) Jesus made this statement to his disciples (his followers), so that they knew the only way to be in relationship with God was through Him.
Why Jesus? Because He is God's Son and the only person who lived a sinless life. "For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life." John 3:16 (ESV)
Why did Jesus die? Romans 3:23 says, "for all have sinned and fall short of the glory of God." This means that we were all born with sin, and we all personally choose to sin, and our sin separates us from God. Not only that, because of our sin, we all deserve death and separation from God.
Knowing that the punishment for our sins could not be removed from us by doing good deeds, God had a plan. He sent Jesus to earth to live a perfect, sinless life and to sacrifice his life on a cross for our sins.
Not only that, after Jesus died, he rose three days later from the grave, showing that He had power over life and death.