Yes, I'm talking about the equalizer in iTunes. If you're playing a CD with another player, then it's possible that it has equalisation (or other signal processing) on, and iTunes' equaliser is off, or vice versa.
Try this - it's possible to play a CD in iTunes by inserting it while iTunes is open, and then playing it as you would ripped music - the inseerted CD will display half way down the bar on the left. I would first see how that sounds compared with the same CD ripped to lossless and see if they sound the same (using iTunes only). If they do sound the same, the problem is not specifically with iTunes but the difference between how the default CD player and iTunes are set up - it's possible that the equalisations are wildly different, or the default cd player has weird signal processing going on, which explains the difference in sound - the point then is to get the equalisation on iTunes correct for your system (ideally it would be turned off, but that may not give the most acceptable sound given your setup).