(Although the question is primarily regarding the post-Talmudic era, this answer includes the general topic of permissibility of later authorities to argue on earlier ones, since I believe it is necessary to give the answer in the context of the broader picture.)
Torah Shebaal Peh was transmitted in various different "Tekufos" - time periods. Very roughly speaking, we have the Tanaim, Amoroim, Rabanon Sevurai, Gaonim, Rishonim and Achronim. Generally speaking, members of a single Tekufah may argue with their counterparts in the same Tekufa, but not with an earlier time period. This is quite a strict rule with regards to Amoraim vs. Tanaim and comes up countless times in the Gemora (e.g. Shabbos 64b, Taanis 14b, Baba Metzia 5a, Kesubos 8a). Similarly, after the Gemora was concluded we are not allowed to argue with it (see for example the Rambam's Hakdoma to Mishneh Torah).
Later on, this is not as clear cut - it's a subject of much debate whether Achronim may argue against Rishonim. The Alshich (Shu"t Alshich Siman 39) and R. Moshe Alshakar (Teshuvot Maharam Alshakar Siman 54) [both cited in Shach CM 25:22] write that just as a Tanna may not argue against an Amora, an Achron may not argue against a Rishon (R' Moshe Alshakar writes that the comparison between his generation and that of the Rishonim is not even like that between a human and a monkey!). However the Rama (CM 25:2) writes in the name of the Maharik (Shoresh 96) that we follow the later opinion if the earlier one was well known. The Shach (Kitzur Hanhagos Issur Heheter 8) brings this and then writes that some argue that we should not follow later opinions which are contrary to the notable Rishonim and concludes that in cases were the earlier opinion is stricter we should follow it. It's also not so clear exactly when the cut off date is between Rishonim and Achronim (somewhere around the time of Shulchan Aruch). What is certain is that there is a veneration of the Rishonim - even those who maintain it is permissible to disagree will do so in a most respectful manner.
Why this is so is quite clear: Yeridos Hadoros. The Gemora in several instances makes mention of the fact that as generations proceed we are not as great as before. (See for example Brochos 20a, 35b, Shabbos 112b, Eiruvin 53a, Yoma 53a, Niddah 24b). This trend continues post Talmud as is evident from the Rishonim and Achronim who say countless times that "Kama'i Adifa" - earlier Sages are greater.
Additionally there are certain cutoff dates when it was accepted that henceforth they would not argue on previous generations. The Kesef Mishna (Hilchos Mamrim 2:1) explains that although Rambam maintains that "the judge who exists at that time" (Devorim 17:9) may overrule previous decisions, once the Mishna was completed it was universally accepted that no later generations would revoke its decisions, and similarly once the Gemora was complete, no person may disagree. The Maharam Alshakar (ibid) quotes the Raavad that one who argues against a Gaon is like arguing against the Talmud, and the Alshich (ibid) compares the difference between Tosfos and the Maharik to that of a Tanna and Amorah.
The question posed a very strong point: "In most other intellectual disciplines we assume that those who come later have the benefit of more information, better access to resources, and the 20/20 hindsight of seeing the errors of those before them. For example today we may have the benefit of materials the Rishonim were never aware of." This is a very valid idea acknowledged in Halachic methodology - "Halacha Kebasrai". (See Rif Eurivin 35a, Tosfos Kidushin 45b "Haveh Uvda", Rosh Sanhedrin 4:6 for just some examples. It is codified by the Rama in Shulchan Aruch CM 25:2). Being that later Sages were aware of the preexisting opinions and still chose to argue we give greater credence to the latter authorities.
However, it is important to emphasize that this is not due to any intrinsic advantage of the later authorities. Rather it is a technical advantage due to the fact that they happened to live later. So, there is an intellectual advantage to being earlier, and a technical advantage of coming later. This already explains the veneration we have for earlier generations; although we may have access to more data than them, we still have the utmost respect for their incomparable level of understanding. Additionally, there will be times when the rule that a later generation may not argue against an earlier one will take precedence over the rule of "Halacha Kebasrai". Thus, we rule like the Talmud Bavli over the Yerushalmi, but a Rishon will never argue against the Talmud. (This is as mentioned above much clearer earlier on, and as we come closer to our times the cut-off points become much blurrier).
The Shibaley Haleket brings a parable from R' Yeshaya Mitrani (author of Tosfos Harid) that expresses this point beautifully: A giant is taller and therefore able to see further than a midget. Yet, if you put the midget on the shoulders of the giant - he will be able to see further. This is not because he is greater, rather because he is building upon what came before him. (The Chavos Da'as (in his Hakdoma to YD) takes this one step further: this would be be true if the giant and midget had equal eyesight. However nowadays even our sight is impaired and it doesn't help that we are "on the shoulders of giants").
For further reading, see the two volume set "Hamachlokes B'halacha", which compiles the views of many poskim on Halachic disputes.
