I think the portrayal problem goes beyond just the character models. I don't think people have a huge problem with an oversexualized female character who also has a strong role. Look at how accepted Lara Croft was, she was made a female role model even though it's physically impossible for any woman with all internal organs in the correct places to look like her.
I think the issue is around games like Rumble Roses or DoA: Beach Volleyball. These are games that have been solely designed to sexualize the female characters, and the end result looks like the game was actually designed around the characters, instead of vice versa. The developers sat down and thought of a way to maximize the suggestiveness of the game instead of trying to make it a great game first and foremost (not that some of these types of games aren't good, which adds another layer to the issue). But, in the case of Tomb Raider, the lead character was originally going to be male, and it was only late in the design that Lara Croft was created. Thus, the game was centered around the gameplay primarily, not how to maximize T&A time (not that that didn't eventually happen).
Or, look at the ads that came out for Bloodrayne 2. They purposefully appealed to the character's sexuality. She was in Playboy for chrissakes, and make no mistake, that was just a huge ad for the game that people paid for. The ads for that game invariably told little or nothing about the game itself, instead showing the digital voluptuousness of Rayne. Big surprise, then, that the action itself turned out to be second-rate.
Which brings me to another point. The developers have something here. Bloodrayne 2 sold a lot of copies, and wasn't that good of a game. The Guy Game sold a lot of copies, and was a terrible game. As much as we can say "this is bad, it's stupid, and it objectifies women", it seems that the game playing audience will buy these games, regardless of how good they are! That's sad, for two reasons; because we really like to stress that good gameplay can make or break a game, and because it seems to put those of us who don't get sucked into the hype in a position where we appear not to understand the market. For those of us who write reviews, that's a bad thing; we should always be aware of trends and the desires of the audience.
So, it's not just having scantily clad women of unrealistic physical propotions that's at issue, it's primarily how they are portrayed as characters and the context they are placed into relative to the game itself.