2008-2011 was great for most parts with some really great performances popping up. First half of 2013 I still think was good but after the Europe leg it just went south completely. Since then no one can honstly say they enjoy a Jon Bon Jovi vocal. It's just not there and there are really no signs it will come back.
When he had his dip in 2003 he still had the tone, that was just a matter of learning how to reach high notes again. It's a different situaton now, he has lost everything that made him great, the power, the register, the rasp.