If you live in 2007, maybe, but now? No, not at all. Most multiplatform companies are doing very well with the PS3, now... very well. This issue is Bethesda's fault, not some inherent fault of the platform. That's like saying crappy ports to the PC are crappy because it's a problem with PCs. It's not.
I agree with you but have to add a few caveats. Ultimately, Beth developed this game and wrote the code for it, so they have to take issue with fixing it on the PS3 especially, so in that I agree with you; they have a lot at stake on that platform since it has sold very well on it. Anyway, the PS3 still is a very difficult platform to make games for from scratch, unless you're studio that works with the system specifically (like Naughty Dog). The problem is the 360 was the lead hardware for making the game, then ported. The 360 is much more similar to a PC than the PS3's CPU architecture is. What Beth should have done, even if it cost more money, is to make the game separately for each console platform. Oblivion for the PS3 was a whole different game designed specifically for it, and not ported, though it still had issues. It played very well in most respects.
Also, the "multiplatform companies" you mentioned have typically made separate developments for each console on typically the first of a series. COD:MW was designed for each system, once it was polished, they were able to port one to the other certain aspects, saving money while ensuing releases were easy to do, because the engine didn't change. It's when the game is ported that it typically does poorly, mainly 360 to PS3, but if the PS3 is the lead, it really doesn't have much of an effect for poorer quality going to the 360.
Two other game anologies;
Mass Effect 2 for the PS3 was released a year after the 360 version so Bioware could specifically work with the PS3 hardware. It has a different engine aspects and played very well, though there were some issues.
Bayonetta, the 360 was the lead platform with Platinum Games, while Sega did the port to the PS3 from the 360 version and it was a train wreck with pretty scathing reviews, while the 360 version got rave reviews. While I do think the game makers should take responsibility, you can bet Sony will be ditching the Cell processor for use in the PS4.
EDITED: for clarification.