It really depends on what you are using your display for, what your criteria is etc.
I've been a plasma fan for many years and own one of the first great plasmas produced (a 4th gen Panasonic plasma - still looks great!). In fact I'd figured through the years I was going to upgrade my plasma image size because I favoured the plasma images over any other technology. But by the time I could afford a 50" plasma upgrade the 60" models had come along and they made the 50" look small. Then when I had money for the 60" the 65" came along and made the 60" look small. Then I waited for 1080p 65" and while I was doing so front projection got better by leaps and bounds (especially in contrast and black levels, not to mention resolution). Once I saw how stunning a big front projected image could look I was hooked.
If you place a plasma right near a front projected image the plasma will certainly "win" in terms of brightness, image punch and (to me) pure realism (with the best of the breed, properly calibrated). But you won't get that cinematic vibe or impact of a truly big image.
With a good projector you aren't sitting there comparing it to a plasma and the image looks fabulous AND you are immersed into the image far more than with any (affordable) flat panel.
So for me, since I am a movie buff primarily I prefer a front projector over a plasma. But there is no denying that getting a top quality image out of a front projector makes WAY more demands than a plasma, in terms of decor, light control etc. You can certainly buy even a fairly cheap front projector and get big screen thrills. In fact my brother in law who had been lauding his new LCD TV took a look at Transformers projected on my bare wall using a super cheap data-presentation projector (that I'm using to size screens with).
He was actually blown away by the experience and walked out swearing to purchase a projector.
Once you get used to a really large front projected image size even those big 65" plasmas look teeny, like "TV" vs "The Movies."
But if you mostly watch TV and sports, need a single display that is flexible, plasma wins.
Rich H.