This would inflate the popularity of a language in proportion to its verbosity, but that could be approximately normalized by using line count ratios from the Great Language Shootout, which explicitly tracks how many lines various languages use to solve the same problem. Precision is pointless--the line ratios vary from problem to problem--but a rough approximation would be useful as long as you could get the statistics with and without it.

I think number of contributors would be a good metric, even though it penalizes lone projects, but I suspect that would be relatively even across languages compared to other metrics. For example, LoC is proportional to verbosity. Commit count is emphasizes languages that tend to have more bugs.

The problem is that one language might require less lines of code to achieve something of the same size/complexity of another language, if it's terser.