Matthew 7:13-14(NIV)

13 “Enter through the narrow gate. For wide is the gate and broad is the road that leads to destruction, and many enter through it. 14 But small is the gate and narrow the road that leads to life, and only a few find it.

I know this will be controversial, and I'm sorry, but it's in the Bible (Romans 1:16)

Jesus is the only way to heaven - there aren't any back doors or "Good People Free Passes". He died for us - imagine if God then let just anyone live eternally after all Jesus suffered. Our responsibility is to make sure everyone knows so that as many people as possible can be saved! God doesn't want anyone to die, so he's giving us grace and time to spread the good news. (1 Peter something)