Objectively speaking, I'd say no. Maybe if you included freeware in the mix, this could be the case, but OSS alone sometimes fall short in front of shareware or commercial apps. Wether people screams that this or that app is far better than the evil closed source counterpart, if you compare both with a cold mind, almost all times the payware software advantages pay by themselves.
Of course, there are exceptions. Firefox is the best example. Of course, it benefits from the fact that most other browsers are free to use, and the only payware worth mentioning, OmniWeb and NetCaptor, have it share of problems.
OmniWeb is limited to Mac OS X, and was essentially pushed back to obscurity by the Gecko-based browsers (Camino and Firefox) and Safari, both options doing more than what people needs, even if OmniWeb packs in more features (for the record, Safari at first was going to be based in the OmniWeb engine, as Steve Jobs made a buyout offer to the company developing it, but the guys said 'no', and Apple turned to KHTML).
NetCaptor, in the other hand, apart from being limited to Windows, it's an IE shell, and a payware one, so despite making inroads years ago, I'd say it's no longer in the playfield.
So, apart from the points mentioned by mouser, Firefox benefits from a propitious software ecosystem. And you don't have too many other open source apps so capable of beating commercial ones. Of course, AutoHotkey and AutoIt are the best in their field, but AFAIK there are no other options (open source, shareware, donationware, or whatever other license you can come up with). Old systems emulators (VMs aside) is ruled by open source apps, and the scene mostly stays away and heavily criticize commercial ones (for obvious reasons). Amarok, although it has been accused of bloatware, it's quite more lean than those heavy commercial jukeboxes (J River and the like) and packs a good deal of features to compete with them. Another field with quite good OSS is development, with the likes of Eclipse, CodeBlocks and all other IDEs and compilers like GCC. Then multiprotocol IM apps, with Miranda, Kopete and Pidgin (maybe...).
The rest can give a good fight to commercial software, but I wouldn't say they're "better" by definition, and they fall in the personal choice camp.
So there you have it, short and to the point