Of the three "giants" of classical music... Bach, Mozart, and Beethoven... I probably listen to Beethoven the least. Perhaps this is due to all those Beethoven fanboys I met over the years on Classical Music forums who were certain Beethoven was unassailable while Mozart was lightweight, and Schubert next to nothing. Most of them rarely listened to vocal music and so missed out on Mozart's operas and choral works and Schubert's lieder which were at the heart of their oeuvres. It may also be that as I came to classical music through my mother who was a soprano in the Lutheran church choir, I have a great love of vocal music... and Beethoven's oeuvre is sparse in this genre... at least in comparison to Bach and Mozart. Whatever. I still listen to a hell of a lot of Beethoven... and these two piano concertos are among the finest ever penned and Gilels' performance of them is among the finest ever recorded.
Of the three giants, Beethoven is in some ways the most "abstract," even though his music often has non-musical sources and references. He composed quite a lot of vocal music, but relatively little of it is still played, and it was probably not his strongest point. It is his mastery of "pure", instrumental music that he is chiefly revered for.
He was perhaps one of the first composers to understand that orchestration is a thing. When Mozart needed a flute concerto, he had no compunctions about transcribing an oboe concerto for flute. But when Beethoven specifies oboe, you need an oboe. Even more so when he insists on contrabassoon or piccolo. He also seems to have been very forward-looking with this stuff, and kind of counted on better pianos being produced - you actually can't really play stuff like the Hammerklavier on an 18th century fortepiano. Similarly, you need a decent orchestra - good luck performing one of his symphonies with the local high school band.
I sometimes get the impression that he knew full well vocal music wasn't his strongest point, and instead of letting it go he kept on hammering away at it, laboring for years, through one version of Fidelio after the other, attempting to do what Mozart seemed to glide through so effortlessly. He pretty much invented the notion of a song cycle, but can
An die ferne Geliebte compare to Schubert's work in this genre? And can
Missa Solemnis, as great as it is, compare to the better examples of the genre by some other composers?
I am always somewhat in two minds about Beethoven, and I think I know why: the man is
exhausting, at least from his middle period onward. Thus, when I have the energy, I think he's the greatest musical genius who ever walked this earth. But only when I have the energy. Nowadays, I mostly listen to his first period works, almost all of which are masterpieces in their own right, but do not carry so heavily on their own weighty message.