Do You Have To Be First Or Can You Just Be Really Good?

I was worrying this morning because some of the things I'm working on now are not the first of it's kind and in social media, that can be bad. In the online world for the last year or so startups pop up every day touting the newest and best and after a while, you just assume that you must be first (or really close to first) to stay ahead of the game. For example, look at sites like Twitter or Facebook that rely on member numbers to stay on top and you can see why everyone's in a giant hurry to get people using their products. If you can come up with it (or steal it quickly), you're well on your way to success.
Look at websites like Skittles that do the online stunt first and get a ton of press/traffic/cool points for it.Who has done the Twitter feed stunt after Skittles? Lots of people. Can you name them? No.
Unless success isn't necessarily selling to Google or causing an online yap-fest.
What if success is looking at a particularly effective online initiative you've done and breaking out in a huge smile because it was great fun to come up with, achieved the goal, and it was well executed?
Then what?
Then maybe being first isn't what you want to be. I have found myself saying over and over the last few weeks the following statement: "You can do it fast or you can do it right." I don't know where I got this grandma-ism or why I've felt the need to repeat it about almost everything lately or if it's even true but I'm starting to believe it.
Maybe I just work really slow and need a good excuse.
This really worries me because businesses that make millions are generally first. Then I started thinking that it depends on the industry. Industries that have ideas and concepts at their core must be really good where inventions and tools must be first. Let's take a look:

Fashion - You must be really good. Sienna Miller wasn't the first to wear slouchy boots, she just wore them really well. And Kate Moss never really designs anything new now does she? The fashion forwards just come up with good concepts and total pictures regardless of whether or not they make them up.
Tech - first. If you build something new and exiting and people come and hang out there you win. Game over competition.
Marketing - You've got to be good. Bad marketing ideas fail to achieve the objective in a way that makes sense. Consistently good shops get the great clients and one hit wonder publicity stunt teams come and go.

I'm still not sure where I stand in the whole first or best feud yet but it's certainly an interesting concept to become re-aware of after spending time in a field that is blending tech and marketing so continuously that it's easy to see two camps emerging and how they are affecting business styles. Thoughts? First or best?