De gustibus non est disputandum.
These matters can neither be right nor wrong. We shouldn't argue as though they could be.
It is a literal impossibility to have poor choice in music. Just as it is impossible to have poor choice in food styles, color preference, or any form of expression from which we draw from. It can not and should not be argued. Have your opinion and express it; as long as you understand that is all it is.
As to the popularity driving our choices, 20 years ago I would have agreed that we could only find music that was most heavily produced and promoted. It still isn't easy to reach the top still but we have many choices for outlets. Not to mention the rapid changes in music in the last 100 or even 50 years. Just compare the indie scenes of the past to now. Getting anything other than chart toppers was impossible earlier but it is fairly easy now. Popular opinion nor technical details are relevant to our choices now. I have a crap ton of cds, vinyl records, 8-tracks, and cassettes that haven't see the light of day in 8 years or more. Most of us get it through a PC now so we have more choices from which we chose. If you are not taking advantage of that then it is your own fault for not trying something new. You will never find what you do like without finding things you do not.
We all have our ideas of what we like and do not like and there is zero reason to convince or even expect others to match our own tastes. You should also pay equal respect to those who have differing opinions. You never know what you may come to appreciate when you give it a try. My music library of 35,000 songs is proof of it, you will find everything in there (except southern gospel).
Eminem songs on CoD I can't say it would really do much for me. I'd say it would hype me up a little bit but I usually get shot in the head every 20 seconds anyways, so I don't believe the adrenaline would do me much good.
As to the music theory statements.
Warning: Spoiler! (Click to show)
You will find that a large majority of people have a decent understanding of it without having ever studied it formally. Our reactions and emotions elicited are nearly universal. We know when an artist is expressing happiness, sadness, or even fear (Devils Tritone). Now granted the majority of people couldn't explain why or what causes it, but we all have an understanding.
For reference I had close to 12 years of experience in music with everything from small backwoods band classes and gym performances to full professional orchestra/symphony and DCI with audiences reaching the 100K mark (even more if you count Macy's day parade). I was ranked in the top 5% of percussionists in GA and could play 95% of all percussion instruments. I'd say I have a strong understanding of music theory. I could play anything you ever put in front of me and tell you all about it, but I could never compose or write anything beyond drumlines cadence myself as I have the creativity of a brick in that regard.
Music theory may or may not improve an artist. You'll get a lot further on creativity and style than theory.