I'm far from an expert on either Bavli or Yerushalmi. But, I'm curious as to why yeshivot (and, to an extent, even individual adults learning by themselves, chevruta or via shiurim) study Bavli far more than Yerushalmi. Come to think of it, I'm unaware that there is a Yerushalmi "Daf Yomi cycle" similar to the one established by the Agudah for the Bavli.
Why is Bavli given more importance? Maybe this is "historical"?
In their introduction to Yerushalmi Brachot, artscroll adress this question and write that Bavli is better edited, more complete, better commented, easier to understand and less prone to alternative readings.
They note that
The period of the Bavli lasted 150 years more than the Yerushalmi, allowing the former to be redacted, edited, its text refined and its rulings refined and clarified. This had not been possible for Yerushalmi
As a result the Bavli was intensively studied and commented on while the Yerushalmi remained a closed book to all but the most accomplished scholars
They detail the specific challenges of learning Talmud Yerushalmi
Its text is generally more terse than that of Bavli. Where the Bavli will often expand upon a statement or proof to explain its points, the Yerushalmi will leave out such elaboration
The give and take of a sugya is generally shorter in Yerushalmi than in Bavli making it that much more difficult to extract the underlying logic and concepts of a given issue
The correct reading of many passages is open to questions and the printed texts are often clearly deficient (and it doesn't have the same amount of commentators having long ago resolved these difficulties)
They comment that no absence is more keenly felt on Yerushalmi than Rashi. His concise illuminations of virtually every statement and his elucidations of the literal meanings of words and phrases are so much taken for granted that few are even aware of how unclear many Talmudic passages would be without his comments. In Yerushalmi none of the commentators attained the same universal acceptance, thus there are many passages of Yerushalmi where commentators offer widely different explanations.
Nowadays though there is renewed interest in learning Yerushalmi, especially since Seder Zeraim (outside of Brachot) has no Bavli and is increasingly relevant to the large number of Jews living in Eretz Israel because of its agricultural laws.
The simple reason is because the halacha often follows the Bavli! It seems more practical to have a student in yeshiva to study something more applicable than something that doesn't apply.
(Of course, I'm not suggesting the Yerushalmi has no worth, just if you can only study one, you ought to study the one more applicable to you, no?)
The Bavli was compiled later than the Yerushalmi by about 150 years, so it's more concise, and it also has a wider range of halachos, containing more masechtos than the Yerushalmi. There are also way more commentaries on the Bavli than there are on the Yerushalmi, to use as aid in study.
As brought up by Matt in the comments, there is a Yerushalmi Daf Yomi cycle, it's just nearly as popular or well-known as its Bavli counterpart.
Addressing the related question of why the Yerushalmi wasn't [yet] translated, Professor Louis Ginzberg wrote (my emphasis):
Shu"t Ma'aneh Levi p. 266
When the Palestenian Talmud was compiled about the middle of the 4th Century, great persecutions of the Jews took place, in consequence of which the leading academies in Palestine were closed and the scholars fled to Babylonia. Consequently, the Babylonian Talmud is in a certain sense the continuation of the Palestinian Talmud and hence of paramount influence upon the later development of Judaism. At the time of the rise of Jewish life in Europe, Palestine had long ceased to be the seat of Jewish culture, while Babylonia had taken its place. Thus it was the Babylonian Talmud that was studied in the schools of Spain, France, and Germany.
In modern times, quite naturally, the Babylonian Talmud was translated into modern languages because it was better known than the Palestinian one.
R' Yoel Lieberman from yeshiva.co brings 3 answers as to why the Bavli takes preference over the Yerushalmi:
1) The Rif in his commentary at the end of Eruvin says that Halachic preference is given to the Bavli because it came after the Yerushlami, and the Amoraim of the Bavli were fluent in the Yerushlami and nonetheless came to there decision which differed from the Yerushlami.
2) Rav Yitchak Isaac Halevi zt"l, in Dorot Rishonim (Chap. 20) offers an historical reason. Based upon Rav Shrira Gaon and Rav Hai Gaon. He says that since there were persecutions on Eretz Yisrael at the time of the compiling of the Yerushlami, the halachic discussions were ended abruptly and did not reach their complete summation. We therefore rely upon the Bavli.
3) The Netziv in his commentary to the Torah, Ha'amek Davar, Shemos 34:1 makes the following novel comment in explaining why the Bavli is preferred even though the Yerushalmi is holier. He compares the two Talmuds to the first and second Luchot. Although, the first Luchot were holier since they were the handiwork of G-d, nonetheless the second Luchot are the ones which remained. Similarly, although the Yerushalmi is holier since it was written by earlier scholars and it has the merit of being written in Eretz Yisrael, nevertheless the Bavli's virtue is that it was able to guide us the darkness of the Galut where the light of Eretz Yisrael did not penetrate. The Talmudic saying in Sanhedrin 24a "He made me dwell in dark places.." This, said R. Yermiah, refers to the Babylonian Talmud", says the Netziv is not a derogatory statement about the Bavli. To the contrary, it comes to teach us that the Bavli was able to enlighten us even in the dark Galut. It should be noted, though that the Rambam showed preference to the Yerushalmi because of its virtue.(See Biurei Hagra, Orach Chaim 235:13)
Some considerations that weren't mentioned:
Yerushalmi is a sort of a Halachic compendium focusing on Halacha, while Bavli is a free-style artwork, covering a much wider spectrum of the Jewish culture, tradition, language, history and more, making it much more fascinating.
The Bavli shows the great flexibility of the Jewish Halachah and the freedom of the Rabbis to bend it in any direction they want by ruling Takkonos over the existing Halochos.
Bavli uses far more disputes and arguments over Yerushalmi, studying Yerushalmi resembles studying the Mishnah while studying Bavli allows for all that "action" we're used to.
Bavli is especially suited for the Exile, adopting the Jewish culture and the Halacha to living amongst Goyim.
Bavli had the "right" to be Halachic "Makeh Bepatish" of the Halacha - finalizing it in many many areas and making its study much more practical.
Bavli contains most of Yerushalmi. While there are many passages in Y. that were omitted in Bavli, basically, Bavli overlaps it.
