Why do people call Bill Belichick a good coach?

As a patriots fan after this past season I personally am fed up with Belichick and am having a hard time understanding why anyone would call this guy a "good" coach in the nfl. What has he done recently but build up a season of promise for us fans only to have his team choke in the playoffs?!?! Plus he's proven to me he can NEVER have a good defense on his ball clubs. The patriots defense continues to suck big time every year giving up huge plays and a lot of yards. He lost the superbowl when the pats were undefeated. And the last 2 years got outcoached by a pair of 2nd year head coaches ( Harbough and Ryan) at HOME, when he has someone like Brady who is suppose to be one of the better QBs. Why does Kraft still have faith in this guy?!? As a patriots fan I think we should do what the chargers did with Marty after they went 14-2 and lost. FIRE HIM! Honestly where do people come off call Bill a good coach when he can't even take good regular seasons and convert them into titles. I'm really starting to lose my patience as a patriots fan!