The gemara says that when Shmuel thought he was being summoned to din he brought Moshe Rabeinu along with him as a prop to indicate that he had not neglected to fulfill anything in Toras Moshe. Tosafos comment that Moshe could not testify to what Shmuel had done during his lifetime because he did not live at the same time as him.
This comment is difficult to understand in light of the sugya in Berachos 18b where the gemara discusses the idea that the dead are aware of what happens in this world. Maharitz Chayes notes this and suggests that the dead are shown what is happening down here but do not have insight into a person's innermost thoughts. Thus, Moshe could not authoritatively say that Shmuel observed the mitzvos that have to do with a person's beliefs and thoughts.
Although the gemara Menachos 29b says that Moshe got a glimpse into Rabi Akiva's classroom, there is no source in shas that I know of to suggest that Moshe saw all generations as Adam did in Sanhedrin 38b (dor dor v'dorshav).
Of note is Tosafos in Shabbos 12b where the gemara says that one who prays in lashon Arami does not have the malachei hashareis aid his tefillos because they don't understand lasho Arami. Tosafos comments that it is odd that the angels wouldn't know lashon arami considering that they even know a person's innermost thoughts. Apparently Tosafos assumes that angels know what we are thinking, but according to Maharitz Chayes (on our sugya) the same is not true of the dead. See also Rav Yakov Emden there who wonders where Tosafos gets this idea from, especially since the angels who came to visit Avraham inquired about Sarah's whereabouts implying that they didn't know where she was. (This is a strange comment considering Rashi on chumash based on the gemara tells us that they knew exactly where she was but were just trying to make her chaviv al ba'alah).