I don't always love Beethoven,as I feel he can be overblown and rambling, but still he is worth listening to for his inimitable ability to capture joy and triumph over darkness (see the ninth symphony for both the best and the worst of Beethoven). One of my favorite pieces from Beethoven is the third movement of his violin concerto, positively soaring in its climax: listen to this Heifetz recording, starting from 7:00. Turn it up LOUD! My favorite way to listen to this is in the car, blasting it. Beethoven was not meant to be played timidly.
I want to like Brahms more than I do, although I really do love his violin concerto, especially the slow movement, so beautiful that it stops your heart. The most glorious section begins right at the soloist's entrance at 2:25, although it's ultimately more satisfying if you allow yourself to listen to the entire orchestral intro that precedes the entrance, as it builds so magnificently. Oy, at 2:36 or so--the gradual rise, the beauty of those singing high notes! Words fail me.
Both of these are far beyond my technical range now or even when I was practicing regularly and taking lessons up until the age of 18 or so. But here's the second movement of the Bach Double Violin Concerto, also stunning, but less demanding, one which I have actually performed with my little sister.
I have also played this. Mozart was a pretty good match for me stylistically at the height of my technical prowess. But watching Hillary Hahn, one of my favorite violinists, perform this with such effortless grace, I am astounded by the gaping chasm between her ability and mine. So here is the principal and lasting result of many years of lessons and unfortunate embarrassments stemming from my laziness: I have come to love this music. Worth it, I think.