To be honest, a lot of developers think they are better than what they actually are (you may or may not fit in to this category).
I have been part of the interviewing/testing process for senior developers, and many who consider themselves senior fall down when asked simple technical questions. This is because people have different interpretations on what constitutes a particular "level". Unlike some professions, there is no prescribed level at which you get promoted up the ranks, the amount of variance in skills and capabilities out there is huge.
To me, a developer should not consider themselves a mid level/intermediate developer until they have been in the business for at least 2 to 3 years, and in that time they have either had more than one job, or have had several roles within the same company. This has got nothing to do with intelligence and capability and specific programming skills, it has to do with experience. You can be the smartest cookie in the packet, but you also need to have experienced lots of different situations and road blocks, and know how to overcome each one in the best way possible. You will not have experienced everything at this stage, but you will have had a good grounding, and be able to use the experience you have to overcome new problems.
More importantly, you cannot take a level of expertise at one place and apply it to the whole market. You may be awesome at your current place of employment, but the standards can be totally different when you step through the doors at someone else's place. You do want to paid for what you are doing though, so if you are doing the work of (what is considered) a senior dev at your current place, then it is only fair you get the same compensation and/or recognition.
In regards to guaging your level of seniority, don't be too fixated on it, because the standards vary so much. I personally think that you need to look at how other industries judge these things. Is a civil enegineer a senior after participating in the building of one bridge? Is a surgeon a senior after just one or two years of operating on people?