Got an example where a commercial product usurped another commercial product's open source project?
Few commercial projects will open source their code, unless they already have reasons to believe that they can't be usurped for one reason or another.
On a market a single law applies: the product that is better marketed wins out.
Eventhough I'd love to see it otherwise, any aesthetical or technical superiority would need to come in enormous figures to even challenge the position of the market leader. For a unsurprising and worn example, look at Microsoft.
On the other hand, if some company takes your code and does better both in marketing and technical aspects, you _should_ lose! The better product is better for everyone in the developer/user base, including you. The community and users don't lose anything -- instead they gain! You do gain as well because you can incorporate the other company's changes back to your own codebase -- of course you did license the software under GPL.
* Where superior here means technically, or aesthetically or friendlier to contributers or whatever.