They are almost identical to my ears too, the songs and productions of the Top 40 songs.makintunes wrote:I do notice, when listening to Top 40 songs, that there are many synth sounds that are almost identical to one another from song to song (at least to my barely trained ears).

In my opinion frequency is one of the most important (and hardest) things to master when it comes to mixing. One thing that's important when it comes to EQ:ing is a good listening environment to be able to hear what you are doing. The first years when I was working with music production I had speakers and headphones which wasn't suitable for mixing purposes. Back then it was hard to do a good mix, even if I suceeded sometimes.
Good luck with your songwriting and mixing!
Best,
Dan