Is Aslan in Narnia supposed to be Jesus?

Yes there is a parallel,

Yes, Aslan is definitely meant to be Jesus in Narnia. When he is sacrificed on the stone table, that is meant to resemble God sacrificing his son, Jesus, on the cross for our sins. That's also why the producers chose a lion to portray Jesus because Messiah, which is a name that Jesus is often called, means King and the lion is the "King" of the Animal Kingdom.

The producers did not decide Aslan being a lion...C.S. Lewis did>