Well, the main thing is that you focus on learning songs all the way through, solos and all, from front to back! With each song that you learn, you will get a lot better, and the things that you learn will apply to tons of songs within a genre...
For example, if you learn the solo for Stairway to Heaven, the same kind of licks can be applied to other classic rock songs in that style, such as Freebird...
It will take time and patience to learn a song all the way through and be able to play it perfectly to the recording, but getting to that point is SO important that I can't stress it enough.
Of course, terms like "intermediate" and "advanced" are relative terms. They depend solely on how "good" the player is using those terms. In other words, something that is hard for one player may be really easy for another. It has more to do with how much you practice; your "learning curve", than how good you are objectively.
That being said, any of the songs from Led Zeppelin, Metallica, etc, provide a good range of intermediate to advanced sections for you to work on. For example, you could just learn the rhythm guitar parts, which would be easier. Or, take the time to learn the lead guitar parts too, which will provide more of a challenge. That's why I stressed learning the whole song!
Some general suggestions would be, in order of objective difficulty: