I have one surface "EG" and two alignments, I'll call 1 and 2. The profile view already has the alignment 1 surface projected on it. I go to profile>Create Surface Profile and select alignment 2, Surface EG, go to ADD it but the profile list is empty. Shouldn't it already be populated with alignment 1 and all I'm doing is adding 2 to it? Both alignments are in the same site.
You can only have one profile view per alignment. So, in this case, you will have two profile views: one for Alignment 1, and a second for Alignment 2. Both will reflect your EG surface as a profile along the length of each alignment.
If you wish the profile created in profile view Alignment 1 to appear in the profile view of Alignment 2 (or vice-versa), you can use the Superimpose Profile command. The results will depend on the relationship between the two alignments. If they are close together, for example, the resultant may be something useful. If they are far apart or otherwise disconnected, the pair in on proifle view might have no useful meaning.
It's what sboon said, with some smoke and mirrors added.
You can only have one profile view per alignment.
You can have as many profile views as you want, but each one can ONLY reference one alignment.