I'm a known proponent of the "Makedon yay!" contingent, on the basis that A) the Seleukids faced multiple major problems on multiple fronts (just as the Antigonids did), and B) the simple POD "No Rome (or anyone else) to spoil the fun" removes or ameliorates many of the issues faced by the Antigonids, but does nothing good for the Seleukids (in the same time-frame, at least). On the contrary, it bolsters their most serious rivals to the West (since without Rome, they don't have to worry about guarding their backs). Thus, I conclude that Makedon is in a strong position, given such a scenario.
As has been noted, the Seleukids could, in an ATL, have done much better. The problem is that they were "one foot in the West, one foot in the East". And this tripped them up, leading to, ah, amputation of the right leg, and that was it for them. No matter what else, their balancing act made it difficult to commit fully to either Western or Eastern affairs. I don't see them becoming hegemon of the Eastern Med unless the perform very capably against any threats from the East (consistently and from an early stage). It's certainly possible, but it's a different POD.
If the POD is simple "no interference from the West", then Makedon doesn't get screwed over. After a few stumbles, it was well on its way to becoming the undisputed power in its direct neighbourhood (which is why Rome, the Seleukids, and a whole bunch of minor local states all moved against the Antigonids). Seleukid involvement was mostly indirect. Sans Rome, Makedon mops up the minor powers, and we are left with an Eastern Med that features Makedon, Aigyptos and the Seleukid Empire, plus some second-rate powers that may have serious potential. (Looking at you, Pontos.)
Aigyptos was in a death spiral, and Makedon and the Seleukids would both be looking to be the hungry vulture there. The fact of the matter is that Makedon would probably be a less direct overlord -- more of a distant suzerain -- and I give Makedon the best chances to basically fill Rome's shoes here. Additionally, this would be after Makedon consolidated its own neighbourhood, while tensions for the Seleukids are only increasing over time. Makedon would be relatively free to act, while the Seleukids would be seriously exposing themselves in the East by aggressively commiting to substantial operations in the West.
If its trajectory is anything like in OTL, I'd say the runner-up is actually Pontos, which can play its card right and come out on top. It's still ascendant for the longest time, and not ready to take on the bigger players. But when the end draws near, it may well seek to play the Antigonids and the Seleukids against each other, exhausting both before pouncing on its own behalf.
tl;dr -- Makedon's chances are often severely under-rated, because people don't care to notice how much Rome's involvement screwed them over. The Seleukids have a built-in weakness of the same nature (the "two-front problem"), but solving it requires an alternative POD. This means that removing Rome gives Makedon the edge. Aigyptos, meanwhile, is on the decline. Pontos is on the ascent, so look there for a cool dark horse. None of the other minor powers really have what it takes.
