I like Strauss too but I suspect Stravinsky is considered to be "higher-rated" but this is just a guess on my part.
I also like Mussorgsky but again IMHO I suppose he aint in the same league as your "3M" conglomerate.
My "Big R" would have to be Rossini.
Have you seen this movie? It's really good!
I have a thread on the go here featuring Classic Rock & Roll in which other types of Music do get mentioned from time to time and so I thought why not go with a thread for Classical Music as well. So I listed the " Big 3-B Names ", then we also have the " Big 3-M Names " with Mozart, Mendelssohn & Mahler. Of course we must add the " Big-T " as in Tchaikovsky, the " Big-H " as in Hayden and many many others. My favourite " Big-S " name would have to be Johann Strauss Junior as his Waltzes are such happy tunes. When I hear such Music as The Emperor Waltz, The Blue Danube or Wine Women & Song I cannot help but get into a good mood.