I'm not planning on talking about comics much, but in the process of working down my comic backlog, I've just finished reading both DC's Final Crisis and Marvel's Secret Invasion, so I feel compelled to compare the two.
Now, to get my bias out right away, I am a much bigger DC fan than Marvel fan. I loved Marvel Comics when I was a teenager (way back when they decided to expand their popular X-Men comic with a new spin-off called The New Mutants, to give you a timeframe). But one by one I lost interest in my Marvel titles, and when I did get drawn back into super hero comics years later it was with the Death of Superman storyline, and I found I really enjoyed the new DC Universe. I still read Marvel books, but ever since then Marvel's been firmly in second place.
So I guess it's going to be pretty obvious that for me, the run-away winner in the battle between 2008's Mega-Crossovers is... Marvel's SECRET INVASION!
I found DC's Final Crisis to be a confusing mess. The first issue and a half felt like completely unconnected scenes, and I couldn't figure out what it was trying to tell me. And what the heck was up with killing the Martian Manhunter in one panel?!? Rich tells me that Grant Morrison was going for something different, showing that these bad guys were so nasty they could kill a major hero like Martian Manhunter like he was a redshirt. Sorry, but that wasn't what I got out of it. I'm all for new and innovative ways of storytelling, and I'm certainly willing to think and try to piece things together, but I guess this one was just beyond me. Maybe I'm just not intellectual enough. (Oh, look! Knight Rider's on!)
The story started to coalesce by the end of issue 2, but I still felt it was moving slowly. Issues 3 and 4 were more coherant, but not exactly exciting me, and I usually enjoy the New Gods. Issues 5 and 6, when the Anti-Life equation is unleashed, I really enjoyed, but even then I felt like I was missing important parts. (Wait a minute, who's under their control and who isn't? Is that the real Wonder Woman?) And Batman went out in style. Then came issue 7, and I was again left thinking, WTF? And the spin-offs that I've read (Rage of the Red Lanterns, Superman Beyond 3D and Legion of Three Worlds) don't seem to connect with the whole New Gods and building of the Fifth World at all-- the only connection seems to be in the Final Crisis brand name. So overall, I didn't really enjoy it.
Secret Invasion, on the other hand, I loved from beginning to end. It was a fast moving story that felt strongly connected and coherant, and presented a crisis (pardon the word) that shook the entire Marvel Universe. I felt like I was getting the core story in the main comic, without missing a thing, but then I'd see how it affected the entire world in any other Marvel comics I read (particularly She-Hulk). Anytime I felt there were characters I didn't really know, I felt I was given enough backstory in context that I didn't feel lost. Brian Michael Bendis is known for his slow pacing, and I think that the conversation between Jarvis and SHIELD on the deck of the helicarrier didn't need to take three issues, but other than that I felt like I was getting a story. A big-ass story, at that.
As for impact... Final Crisis killed Batman and Martian Manhunter. Secret Invasion killed the Wasp and a bunch of low-tier heroes, most of which I've never heard of anyway. Now I expect all of those main characters to come back (I give Batman 12-18 months, the Wasp 3-5 years, and Martian Manhunter 5-10 years) but it's still a pretty big deal. On the whole, though, even though he got a good death scene, I feel Batman deserves to go out on a better story.
Oh yeah, and we got Barry Allen back. Well, I suppose that will make the old school Flash fans happy. Personally I never really got into the Flash, so all it is to me is another reversal. See above predictions. ;)
I still buy three times as many DC books than Marvel books, and I don't expect that to change any time soon. Still... you know what Marvel's been saying: Embrace Change...