Good enough?

"I'm a good person."

"The message of the cross is fine for murderers and thieves, but I've lived a good life."

"If there is a God, I'm sure He won't punish someone who's been sincere and tried to be the best person they can."

If there was any possible way for a person's goodness to merit salvation, would God have been willing to see His own Son die a horrible death on the cross?

Galations 2:21
I do not set aside the grace of God, for if righteousness could be gained through the law, Christ died for nothing!" (Today's New International Version)

"I do not nullify the grace of God, for if righteousness comes through the Law, then Christ died needlessly." (New American Standard Bible)

I do not treat the grace of God as meaningless. For if keeping the law could make us right with God, then there was no need for Christ to die. (New Living Translation)

I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain. (King James Version)

By saying these things I am not going against God's grace. Just the opposite, if the law could make us right with God, then Christ's death would be useless. (New Century Version)