im wondering what is it!?
...Well, how do you want to measure it? Sales? Amount of merchandise? Longest-running?
The longest-running anime in Japan is a show called Sazae-san. Second is Doraemon, which is also huge in terms of merchandise. They've probably made the most money, but it's by virtue of being around a long time (Sazae-san has literally been running for forty years-- since 1969 --and Doraemon since 1979, not including a brief show that ran in 73.)
Sazae-san still consistently sits towards the top of the Oricon most-watched charts. So it's probably the "most popular" anime overall. But of the two I'd bet that Doraemon has made more money, because it markets itself with merchandise and movies and stuff.