The built in ones are great. The EQII is very decent. But the best Eq IMO is the Maag EQ4. It is really amazing. Also I use apQualizer with the VST to RTAS converter. Very amazing linear phase eq with analyzer and M/S mode. Also look at the PSP sQuad because it's cheap and comes with 4 great eq's.
Here is my must have list of EQs
Maag EQ4 - Mixing Eq
apQualizer Linear Phase Eq - Mastering Eq
Massey VT3 - Crispy Character Eq
Sonnox Eq - Great all purpose eq with different eq models to chose from.
ProTools EQII
Anything from Softube
You need to pay for a great eq. They are worth it. If had to only get one it would prob be the Maag because it is magic but the Sonnox is good anytime.
A great free eq on PC is the Kjearhus stuff.