Sounds like a self-important sort of question from a RPG blogger, doesn't it? Before you jump to conclusions, bear in mind I'm a moderator on two fairly large RPG boards, subscribe to the Imperial Moot, and have joined many different gaming message boards in general. So why am I spending more and more of my time surfing gaming blogs?
Here's the thing: there are some things that message boards are always going to do better in terms of organization or community when compared to blogs. If you don't believe "better", at least "better according to the tastes of many". Threads, private messaging, a single-point community--these are all things RPG forums offer that most blogs don't. But, as has been mentioned in comments here, Whitehall ParaIndustries, theRPGsite, and many other internet locales, there seems to be a popularizing of the RPG blogging community and commentary. I notice more and more esteemed and well-regarded message board posters and publishers striking out for Blogland.
For my part, I know my readership was increasing even before RPG Bloggers Network, the institution I credit for the biggest jump we've seen in cross-pollination and blogging synergy. But personally, I've been spending more time reading gaming blogs at the expense of forums. I just found I like the pace of a blogging community. Many posts seem more well-considered, the pace of discourse is a little slower, a bit more courteous. You don't have to worry as much about the inevitable Gaming Theory/Edition War/Palladium Books threadcrap.
Forum discussion is often more knee-jerk, moderated by a third party who likely won't share your views on what constitutes disorder or off-topic. Arguments blow out of proportion, aided by the twin spectres of "everyone's watching, gotta score points" and "they just know me as OgreTroll_LupinIII! I can free the beast (read: a-hole) within!". At it's best, it can bring together a nice group of regular contributors, who give a great series of opinions over the course of a thread. At worst, it can produce an inbred, toothless "safe haven", where overmoderation leads to sniping, passive-aggressive snipes, and baiting. At blogging's best, it's a community of folks doing their own thing, but learning from other blogs in the community, writing a variety of interesting items with moderation left up to the individual blogs. At worst, it's a widely-scattered, inconvenient mess of folks who can go silent or burn out for weeks at a time.
Honestly, blogs and forums can both be a heaven or hell for gaming. And I still love many of the forums I visit, and wouldn't trade them for the world. But I can't help but notice when I'm surfing the web at night, my blogroll is now my first stop, right after my email. And Webkinz for my daughter.