Kabutops ex should not be on this list. Kabutops/Steelix would be on a list for Neo cards, but this remake did not make the cut in this format. I don't know why but I would guess that the attack damage vs the flips no longer did well because of the higher HP on pokemon-ex.
Sceptile/Slowbro was a fun deck. Should not be on this list.
Slaking/Espeon SS, I never heard of that.
RAMBO and Gardevoir were really the top decks from the prior format, E-On. They survived format rotation and were still played, but in RS-On, ZapTurnDos (later ZRE) would have been the first next big deck, followed by Dragtrode and a clunky version of Rock-Lock with TRR. Ludicolo came next with Deoxys. Rock-Lock got better in the latter part of RS-On and then became good in the next modified. Early in the modified, "Monarchy" was played with but was a failed deck. Later, it would be shown that "Queendom" would have been a better focus due to its success at Worlds but it just didn't get too many looks prior to that (consider how Team magma took everyone by surprise).
I don't know if I would consider Team Magma "good." Yes, it won at worlds but after that it was not really played. It was more like a metagame decision that people were not ready for rather than a deck that proved itself over the course of several tournaments (either before or after). The consensus was that Team Aqua was a better all-around play. At US Nats, one theme deck sealed tournament with Team Aqua and Team Magma decks, Team Aqua was considered superior but in hindsight that was probably because no one knew how to play Team magma and simply let their prejudices win out. Maybe in Japan it did well, but I don't recall seeing it with any consistency at tournaments after Worlds except as a fun deck. Compare this to Queendom which did see play after the Worlds that it did well.
It may be useful to search the featured articles and tournament reports. Unlike older formats, this one and the one after it began a time of well-documentation of what was played. in articles, people will show match-ups, showing what decks were most likely to be faced (and therefore popular) as well as some random rogues.
