There are several places in the Gemara where a person "argues" with G-d. You are probably referring, however, to the Gemara in Bava Metzia 59b, which details at length an incident in which one rabbi, Rebbi Eliezer, debated with all of the other rabbis on a certain issue. Even though a heavenly voice issued forth during the debate proclaiming that "the law follows him in all places," Rebbi Yehoshua stood up and declared that "it is not in Heaven" (Devarim 30:12), but rather G-d commanded in the Torah "the matter must be decided by the majority" (Shemos 23:2), meaning that in cases of a debate about the application of a Torah law, the Halachah must be decided by humans based on the guidelines given by G-d at Sinai. It is G-d's will that the Sages apply the laws of the Torah to the best of their understanding. Rebbi Yehoshua was saying that this means that G-d does not involve Himself, so to speak, with deciding questions of how to apply the Halachah. How, then, did he explain the fact that a heavenly voice issued forth proclaiming the Halachah to follow Rebbi Eliezer? He understood it to be merely a test of whether the Sages would properly fulfill the requirement to rule in accordance with the majority (see Rabeinu Chananel cited by the Shitah Mekubetzes.)

The Gemara there continues and says that Rebbi Nasan once met Eliyahu and asked him, "What was the Holy One, Blessed is He, doing at that moment [when Rebbi Yehoshua rejected the heavenly voice]?" Eliyahu replied, "He (G-d) was smiling and saying, 'My children have won over Me, My children have won over Me."

The Sefer ha'Chinuch (#496) explains what "winning over" G-d means. G-d decreed that it must be human authorities who decide the Halachah based on the guidelines that He gave at Sinai, such as the guideline that the Halachah follows the majority opinion. Furthermore, part of this decree is that the majority's decision will stand even in the rare case that it is a mistake. The reason for this is that since humans do not have perfect, Divine intellect, mistakes in applications of Halachah are inevitable, and thus -- if it is left to individuals to decide how to apply the Halachah -- there is a risk that different people would decide how to apply the Halachah in different ways, and the Torah would be practiced differently by different groups. To avoid such a situation, G-d gave to the Sages the prerogative and responsibility to decide Halachic questions. Even though, being human, they, too, are prone to make mistakes, the disadvantage of an occasional mistake is far outweighed by the advantage of having one group with the authority to decide Halachic issues and the entire nation practicing the Torah in a unified fashion.

In the incident that the Gemara relates, since the Sages rejected the heavenly voice and insisted that the Halachah follow the majority, they used G-d's own rule to enforce their ruling (which may very well have been a mistake) and in a sense "won over" G-d. G-d therefore smiled, as it were, saying that "they used My own rule in order to win over the truth! Nevertheless, their mistaken decision will be upheld as the Halachah in this one case for the sake of the eternal authority of the Torah."

Y. Shaw