Of course there are a myriad ways to measure succes of each Wikipedia.
For what it's worth I tried to establish the ratio of active contributors per million internet users that speak that language.
So per language the figure shows that one of x thousand native speakers with internet access contributed to Wikipedia in that language
Polish 22 German 31 Dutch 39 Hebrew 40 Danish 44 Swedish 49 Catalan 49 French 49 Finnish 51 English 53 Norwegian 55 Hungarian 94 Romanian 109 Slovenian 117 Italian 166 Japanese 168 Czech 216 Spanish 236 Vietnamese 367 Greek 386 Portugues 431 Russian 638 Chinese 687 Turkish 725 Arabic 870 Malay 967 Korean 2920
For contributors I used wikistats Feb 26 (counts registered users > 10 edits)
For internet users per language I used figures from Global Reach (2003)
http://global-reach.biz/globstats/index.php3
Of course I don't know how exact these figures are, but I assume they did some homework.
Note : the GR figures list >native< speakers, so actually languages with international appeal would show lower participation ratios (higher numbers in the table) if all web users that might be inclined to use that language were taken into account.
E.g. GR mentions India specifically as a country where the web language is English and not Hindi.
Erik Zachte