I'd say it depends more on the contents of the collectors edition then the game. I mean, if the game is good, I'll buy one of the editions no matter what. If the game sucks, I won't.
It really comes down to if the collectors edition is priced fairly based on what it comes with. New Vegas, for example, came with a sweet deck of cards, some "meh" poker chips (but one big metal one that clinks really loud if you're one of those badasses that sits around flicking a coin all day), a really fucking pretentious and uninformative making of video (I'm sorry, but they just kinda seemed to act like every single thing they couldn't do because of technological limitations, was actually on purpose for artistic value. Also they make it seem like Vegas is way more populated.), and a really short, but really cool graphic novel about what happens right before the game. You get this all for $20, which is relatively close to how much I honestly think it should cost.
But the reason I say not to buy it for the game is because of games like Halo and CoD having these ridiculously expensive editions with just one really cool thing. I got the Halo 3 one because I thought the helmet was cool, and I will never waste that much money again. Just look at Halo and CoD's wallet destroying editions.
Halo 3
Legendary Edition: $130
Extra Stuff (Total - $60): $70
Specific Extra Contents (and estimated cost):
-1 Silly Helmet that has been sitting in my room for years. ($20)
-1 Making of DVD (Free Online)
Amount Overpaid (Extra Price - Total Estimated Cost): $50
Halo Reach
Legendary Edition: $150... WTF!?
Extra Stuff: $90!!!
Specific Extra Contents:
-4 or 5 Fucking MacFarlane Action Figures ($40 bucks tops)
-Flaming Spartan Helmet (Useless in game aesthetic, plus it gets you killed and shows you're either a rich douche or your parents bought the game for you so $0)
-Extra Elite Armor (Useless in game aesthetic that is barely used... maybe $5)
-A couple of stupid documents (Free Online)
Amount Overpaid: $45
Call of Duty: Modern Warfare 2
Prestige Edition: $150... AGAIN WTF!?
Extra Stuff: $90
Specific Extra Contents:
-Artbook (Free Online)
-Original Call of Duty (Free on PC... but for the non-pirates I'll say $5)
-Night Vision Goggles (Can only see up to 50 ft... WTF... I'll be generous and say $60 dollars tops)
Amount Overpaid: $25
So yeah, don't let your fanboyness convince you into buying this crap.