I've seen both play out many times in real life and personally I prefer sticking to celebrating results. Why celebrate hard work just for the sake of work? shudder
Why do hard work at all? My answer would be to risk building something great. I doubt anyone wants to do hard work for the sake of it. Building a culture that rewards honest effort would encourage the same hard work in the future despite risks of failure -- though admittedly it's easy to go overboard in either direction! Use your best judgement here.
I realize it might also be easy to extrapolate this out to always rewarding a team, no matter what, and I don't want to suggest that in all circumstances... you know if your team put forth an honest effort and should be rewarded despite building something that fails. Definitely don't mean for this to be a hard and fast rule, but more of a tip for encouraging a smart, hard-working team to feel safer taking risks.
What if the reverse advice (acknowledge only results, not mere effort) were given to parents and teachers instead? Then perhaps the next generation wouldn't need their managers to celebrate effort in addition to results. Edit: And why is this desirable? Because the market itself only rewards results, not effort.