@Krishna The album in your avatar is an example of a bad mix job. I'm a ATL fan (Black mafia life is a top ten rap album classic IMHO) but that 187um solo was not on par.
Bad mix job? bassline and kick fighting each other. Vocals too low or too high in the song. Ad-lib/background tracks too high or too low. Too much compression (squashing all dynamics) or no compression on vocals or instruments. Without getting too technical you use compression (or limiting) to level the tracks out. Insane use of reverb/delay (these effects should be used so you can BARELY hear them) wrong panning (like panning a pianos high end to the left or panning a kick drum to the right), phase cancellation (listen to a track in stereo and listen in mono sound different?), distortion in the tracks (you'll know it when you hear it), improper use of eq (boosting the wrong frequencies, not cutting the right ones) and 60 cycle hum in the tracks.
Digital distortion and bass distortion are two different things. You can have bass distortion (too much bass especially in the 20hz-110hz range and mud in the 300-500hz range) but no digital distortion. You record too high (over 0 db in the digital realm) and you get digital distortion. You clip the master buss........well.....you get digital distortion.
You have 4 stages:
1. Performence/arrangement
2. tracking/recording
3. mixing
4. mastering
If you mess up in stage 1 it will ruin 2, 3 and 4. If you mess up in stage 2, it will ruin 3 and 4. You mess up in stage 3 stage 4 will be ruined. You have to do each one CORRECTLY when you have the chance. I find a lot of problems come from stage 2. People simply don't track correctly (unity gain/gain staging) and if its not recorded properly it's very hard to mix it. If a track has 60 cycle hum/ line noise you have to take the time to use a gate or some other plugin to reduce the artifacts.
All of this probably wont make sense to you but to some of the people reading this it will. I don't listen to music from a consumer standpoint. Everytime I hear something I'm listening from an engineers standpoint and thats something I can't change. Heres an example. Have you heard the westside connection "terrorist threats" album? Listen to the the terrorist threat song and after that listen to gangsta nation or the first song on the album. Do you hear a difference? The song sounds muffled (they could have WANTED it to sound that way) but I wouldn't have done that. Listen to the games album. Listen to the song before the one eminem did and listen to the one after eminem. What do you hear?
Now I admit NO album is 100% PERFECT (not even dr dre's chronic it had too much reverb for my taste) but some things should NOT be accepted. I had to mix some songs recently that had digital distortion (not recorded at my spot) and I had the artist go back in and re-record the tracks. I had stuff that was sent to me that had 60 cycle hum and too low. I had the producer re record the tracks.
Solution? Work with people who know what to do and when to do it.