In the anime, Mamoru and Usagi didn't find out each other's identities until just before the appearance of the Silver Crystal (after which Mamoru was captured and turned evil). This meant there was absolutely no time for them to form any real relationship until after they had regained their memories. In PGSM, the situation is similar but for quite different reasons. Or rather, reason: Mamoru's engagement to Hina. By contrast, the manga actually does have the opportunity for Usagi and Mamoru to meet on amicable terms, with little complication, before the tragedy which leads to the Silver Crystal appearing. (They meet in the park in manga Act 7, and agree that the next time they meet, he will return her handkerchief, and she will return his watch. The watch is a music box in the anime, and in PGSM there is instead Usagi's hand-made scarf.)

Perhaps more importantly, this episode includes a manga-based plot event that we've been waiting for for a looooong time: The flashback to the Moon Kingdom! However, among other things, the details given in each version of the story are quite different. For a start, both the manga (in Act 8) and the anime make it explicitly clear that it was the Dark Kingdom that attacked in the past, and that this was in order to get hold of the Silver Crystal. Neither of those things have been revealed in PGSM (yet), although of course it doesn't take a genius to make the connection. It also wasn't explained in PGSM that the Silver Crystal was used to seal away the enemy, and that the girls were reborn in order to fight it - Artemis seems to hint at the Sailor Guardians being awoken because they needed to fight, but this is rather vague.

The anime's explanation - at least at this point in the series (Episode 35) - focuses on this sort of thing rather than the love between Prince Endymion and Princess Serenity. However, the manga (in Act 8) elaborates even further than what was said in PGSM. In particular, communication between the Moon and the Earth was forbidden completely, and when war broke out, Endymion was labelled as a traitor for not wanting to take the Silver Crystal along with the other people of Earth.

In PGSM, several characters suggest that Usagi and Mamoru shouldn't be together because their love might cause a catastrophe as it (apparently) did in the past. In the anime and manga, this is not the case. Instead, manga Usagi is glad that she and Mamoru have finally found each other again, and distraught that something so terrible has happened when she still has so much to tell him - and this, specifically, is what causes her to cry, and the Silver Crystal to appear.

As in the anime, Usagi and the others don't really remember anything of their past, and Luna has to give them the aforementioned flashback explanation. In the manga, Usagi and Mamoru instead have their memories return at the same time, upon the appearance of the Silver Crystal. Also, in both the manga and the anime, the apperance of the Silver Crystal was permanent. In PGSM, it appeared once in her tear, but has now gone back into her body again.

As I mentioned in the Act 25 comparison, in both the manga and the anime, Mamoru was kidnapped by the Dark Kingdom and turned evil. (This was kind of different in the anime to in the manga.) In PGSM, this seems to have been split off into the "Evil Mercury" storyline, and Mamoru going to England as a consequence of the Mamoru/Hina storyline. In any case, the bottom line is that the Usagi/Mamoru relationship is out of the picture for a while, as Mamoru is gone.

In the manga, Sailor Venus revealed she was the Princess in Act 8, and then admitted that she was just a decoy Princess in Act 9. In PGSM, there was a lot of time between those events, during which a contemptuous relationship between Sailor Venus and the others was added.

In the anime, Queen Beryl killed Zoisite in Episode 35, for disobeying her orders. He died in the arms of Kunzite (as I've mentioned before, they were lovers in the anime). No such thing happens in the manga (where he died earlier) or PGSM (where he is alive and well).

The general development of the Four Heavenly Kings continues to be very different to in the manga and the anime. In the manga, the light of the Silver Crystal causes Kunzite to regain his memories of the four of them serving Prince Endymion, but being misled by the great evil. They were reborn so they could find their Master, but they fell into evil's clutches again. The light also causes Jadeite, Nephrite and Zoisite to come back to life, but they quickly turn into their respective gemstones (as they did one at a time earlier in PGSM). However, spurred on by Queen Beryl, Kunzite captures Mamoru for her anyway.

In PGSM, on the other hand, both Zoisite and Kunzite have regained certain memories of the past, and this is affecting the the actions they take (as should be clear already, Queen Beryl does not have an authoritarian rule over the Four Heavenly Kings, unlike in the manga and anime).

The anime never establishes that the Four Heavenly Kings were Endymion's subjects, and does not have Kunzite regaining memories at this point in the story.

Anything I haven't mentioned was added for PGSM (I don't think I've missed anything major - feel free to e-mail me if you think I have). PGSM continues to take plot elements from the manga and rework them around its own plot, centred on the friendship of the girls and Usagi's relationship with Mamoru. This continues on into the next series of episodes, where once again, there is very little manga-based plot.