Forums - Worst CTR ever.
directories - If you have traffic, and blend the ads well with links these can do ok.
blogs - bad for adsense, but if you sell ads directly if your blog is a car blog sell ads to car websites etc.
portals - Too broad of a term, some do well.
myspace - Pays horribly, if you have a lot of traffic it ads up.
classified ads - Pretty much a directory, but if its classifieds you can charge for premiums listings.
dating sites - If you can get one going with traffic its best to sell ads direct or go cpm.
tutorials - Never made a site.
article websites - Depending on the articles content this can pay very well.
The biggest thing is traffic. It doesnt matter what other sites do best. If you make a good site, it will get traffic, and will generate revenue.