Some would consider DX being reserved for DC properties to be a dubious kind of honour - as they hate PERS and would rather it be done away with altogether. I'd say many would be thrilled to see 'DX' being taken away and hogged by Marvel (AKA Iron Man)
Eh, I'm of the opinion that, when it works, it works phenomenally (DX 08, DX 09, DX 11, and DX 13), and, when it doesn't, it's normally because they didn't treat it right. Take the DX 12, for example. Announced in July (just in time for TDKR), shipped in November, before the Blu-Ray even came out. The DX 11, on the contrary, was teased over a year before it was announced, and it faced multiple delays. That indicates, to me, at least, that the DX 12 was a rush job, rather than them actually doing it justice. I think it says something that, other than that, and the earliest DX releases, they've all been pretty great, on the DC front.
As for Iron Man, if people are saying that Bane isn't iconic enough, Iron Man most certainly is not, and before someone jumps my **** about that, Iron Man, as I said, was a nobody outside of comics before RDJ. So, I'd argue that they're pretty much on level ground.
Meh, it isn't Marvel's fault DC can't get out of it's own way. Truth is Superman, Batman, and Joker are all stale. DC has gone to well with these same 3 characters in film seemingly 9 million times already. Yes, let's tell the origin story of Superman, Batman and the Joker AGAIN! Is the DC universe that small and/or boring that they can't do anything else?
Marvel killed it with their character's solo films and tied all of their worlds together in the Avengers which was amazing. DC? Not so much. But hey, at least they revealed a new movie at SD Comic Con right? Who's in it you ask? You guessed it: Superman & Batman. Good job DC.
DC? Not so much? Last time I checked, Man of Steel was a commercial success, and a hit with audiences. Even with the "rotten" rating, the majority of those critics liked it (57>43). Why wouldn't they start with Batman and Superman? That's what people have been waiting years to see, isn't it, and the funny thing is that those solo films didn't "kill it" the way you think they did. Outside of Iron Man, they were moderate successes, both critically and commercially. So, pardon me if I find it funny that you're criticizing DC's start.