It all depends on the diver. I did the Speigle Grove in three to four-footers and a stiff current with only 10 ocean dives under my belt with no problems and had a hell of a good time. Next person might need 50 to do the same thing or may never be able to do it at all. It's all subjective.
Garrabo has a great point - simply making it through a number of dives doesn't make you a novice, int. or advanced diver.
Conditions, difficulties you've faced and overcome, and
your personal ability to extract learning experience from them are major factors, and you can't quantify them so easily.
My personal view of this?
Beginner - Someone who feels they need assistance in basic gear set up, or to be guided through dives to feel safe, or has a very narrow range of experience in a single, or nearly single, environment.
Intermediate - A diver who is comfortable with their gear, diving without a guide in environments they are comfortable with, and who, with a buddy, can conduct their own dives per their plan. Can handle "normal" problems during a dive without undue panic, stress, or increased hazard to themselves or their buddies (i.e. mask flood, addressing equipment issues, unexpected changes in the current, tide, etc.).
Advanced - A diver who is comfortable in all fundamentals of diving and related knowledge (i.e. can formulate their own dive plan, gas consumption, NDL information, equipment) and has experience in managing stress situations while diving. Can accurately evaluate the potential hazards of diving in unfamiliar environments and locations. Has all skills of diving down to an intuitive or muscle-memory level. They can be counted on to self rescue in most any situation and address serious changes in the environment while diving with their buddy.
These aren't all inclusive, but when I look at a dive site or potential dive buddy this is how I look at it.