@ Errikos
Since the amount of time required to further engage in detailed discussion of the points you have made has to go into other activities, I'll just sum up what seem to me to be the most important differences between our views on the issue:
a) You consider talent and innate musical personalities as naturally given factors which can be refined, but not developed in the strict sense of the word. I don't - I have no belief in crucial or even dominant importance of any innate talent whatsoever, and believe that what we refer to as talent is essentially developed by a combination of factors, all of which have to be at least partially present to lead to excellent results. To put it short: what you call talent is in my opinion innate only in very limited and elementary sense, the major part of what we understand under talent is actually developed through a combination of experience, skill and acquired insight, theoretical as well as intuitive.
On a sidnote, the examples you bring I find to be unconvincing, as they leave some of the crucial aspects of the whole story aside (Mozart-Mendelssohn-Prokofiev-Chopin starting with the best of the best quality of musical education and guided composition and starting studying musical literature at an extremely early age, that is, amassing a 10 or even 12-year of intensive listening and composing experience until the age of 16 (the same BTW goes for Korngold), Mussorgsky not being self-critical (which is incorrect, Mussorgsky was a vey self-critical composer, the booze notwithstanding), Scriabin talking of his "inertia" etc.)
b) This is, I guess, to a certain amount a level of personal preference: I would gladly give up Chopin's Op.10 for any single one of Taneiev's mature chamber works, Les Troyens, any symphony by Draeseke or any Bruckner symphony beginning with the 1st. I also don't consider Draeseke to be a minor composer: in my opinion, his 2nd and 3rd Symphony (not to forget the Gudrun Ouverture) stand on the same level with the very best of Brahms' symphonic movements, and at times even surpass them in terms of originality of their formal solutions and their motivic intricacies (the 2nd Movement of the 2nd Symphony particularly being a case in point). The same goes for Taneiev, whose best chamber works I find to be no less masterly then any other I know of.
P.S. The assesment of Stravinsky and Bartok as having no melodic gift strikes me as strange - I find many of their melodic as well as harmonic solutions and idiosyncrasies very memorable as well as very refined (not that I could care less if they didn't posess any "melodic gift" at all, as melody is not the dominant or decisive factor in how I percieve music). Beethoven on the other side seems to me also to be quite "unmelodic" in this sense - which, again, doesn't exactly bother me when listening to Diabelli Variations ;-)