which popular ads can be used on most languages?

IMHO you don't want popular ads, you want specialist ads for your niche.

If all you are going to do is build a generic website hoping for lots of traffic and AdSense cash then you do realise the amount of competition you have don't you?

If your site is not in a supported language, then you cannot have adsense on it.

but there are a lot of great websites out there with huge traffics however they can not place popular ads because of the unsupported-language problems.

Which languages are you specifically suggesting?

Which language(s)? If Google doesn't "support" a language, most likely it's because there aren't enough ads to justify it. Just because there's traffic doesn't mean there are advertisers.

Traffic does not equal income. Do not be seduced by traffic. Traffic is meaningless. Focusing on traffic is one of the most common mistakes. HuskyPup's advice is the best, focus on the niche. You will never make decent earnings if you don't stop what you are doing right now and spend at least a few months researching why one site makes money and why another more popular site does not.

You obviously do not understand the fundamentals of building a successful site. You will NOT learn it here in the AdSense forum. This forum is the WORST place to research what makes a site successful. Here is a discussion [webmasterworld.com] that will give you some jumping off points for beginning your research. Good luck.

I believe there are too many language-independent ads out there: such as medicines, cars, international banks, ... etc. It is just unfortunate that google can not handle it all even though they do have most of these languages supported with their translation facility/tools.

@martinibuster
I am going to read it all, thank you for the links ...