Imagine a runner in a race. As he comes around the corner, he trips his first opponent. The next one he shoves into the bleachers. Some other guy he throws dust in his eyes. Then he cuts through middle of the track and pops out just before the finish line. When this runner crosses the finish line, does he win the race? Of course not!
But think of another runner. This runner doesn't trip, doesn't shove, doesn't cut corners. But this runner left the starting line just a split second before the pistol went off. Even if he completes the entire race perfectly, that one little mistake still costs him the race.
This is how it is for all of humanity. We like to think that because there are people in the race of life like the first type, that somehow we might still be rewarded even though we're the second type. But the only person who wins the race is the one who runs it perfectly. We're not graded on a curve; it's either perfection, or it's failure.
Critics of the faith say they don't think it's fair that someone who lives a "good life" goes to hell, while a criminal who lives a terrible life might find Jesus right before his death and be saved. What these people fail to grasp is what we read in Romans 3:10, "There is no righteous person, not even one...". They think that if you do your best, or at least land in the upper half, you should be okay. But if being "good enough" were good enough, God never would have sent Jesus to the cross; the cross was the only way.
All of us have sinned. All of us are imperfect. Jesus is the only one who ever ran the race perfectly, and He's willing to put His medal around our neck. We merely need to bow before Him, confess our sins, admit He's our only hope, and ask for His forgiveness.