He isn't in the top 4 because the top 4 are in the top 4. He's nowhere near their level, even at his best. The current #4, Murray, is better than him. Therefore, he won't get into the top 4 when the lowet ranked player is better than him.
He can definitely be the #5 consistently though if he plays with more consistency.
How ignorant. No surprise though.
Berdych at his best is better than Murray. Most people agree with this. Murray is way more consistent. That's all. Berdych can hit anybody off court on his day. Murray wears down his opponents at his best which is good and of course he is a deserving top 4 player. But stating he is more talented than Berdych is delusional.