I can't really say I've noticed imbalances in the channels in my source material (at least when I look at it on my workstation), however I also notice a generalised bias to the left channel when listening. I can explain a small part of this on account of my hearing. A test I had a few years back showed I had "flat" hearing 0 - 8,000 hz (highest pitch tested) in my right ear - in other words it was at the 0 dBHL mark, but my left ear actually went 5 dB "above" 0 dbHL at 6,000 and 8,000 hz. Apparently it is an unusual result - especially for a male nearly 50, but not unheard of.
But I think more of it has to do with what I listen to (orchestral music) almost exclusively. Many of the instruments over to the left operate at frequencies to which the human ear is more sensitive. Put it this way, you are going to be much more inherently biased to hearing a violin, flute and French horn than you are a tuba or double bass. Infact composers know this and write their music knowing what will "stand out" versus what will simply enhance to the overall sonic soundscape.
It's not like I perceive an actual imbalance that I would want to ever "fix" - it's just the nature of music I believe. Furthermore, if you took all the classical music ever written and collectively analysed it, you'd find more often than not, the principal melodies will come from the left side of the orchestra. That is not to say they do not come from other sections- they obviously do and on a regular basis of course. But take the total number of hours of classical music ever written and surely the first violins on the left hand side have it over all the other sections in terms of total time spent with the main melody.
But the OP should have an audiogram
Just to check that everything is OK. And if it isn't, that is no big deal either. My hearing is not what is was when I was 15 years old and it isn't what it was when I was 30 either. But the brain compensates incredibly well and perhaps if there is a problem, the OP can compensate for it (speaker placement, room treatments, etc).