When considering the impact of new stadia, you have to take into account where the clubs were prior to the stadium being built and will that new ground enable them to compete at a higher level (or better at the same level in the case of top sides).
I'm not sure that ground redevelopments can be factored in here as that would apply to many, many teams.
Incidentally - interesting fact. When Roots Hall was built, we had the most modern ground in the country until Scunthorpe moved to Glanford Park in 1988.
Walsall moved to the Bescot in 1990 and since then, many clubs have re-located.
In the above clubs cases, I would argue that it has left them probably where they were before but in a lot more comfort and able to survive, compete and attract players. Then again, they didn't do a "Darlington" and go from a small, division 4 ground into a bloody great 30k stadium that they would have no hope in hell of filling. The demographic in Darlington means that there probably isn't an event you could put on that would attract 30k people, football related or otherwise. That was madness.
So what of the other clubs that have had new grounds? Has it helped them?
As said earlier in this thread, Swansea, Reading, Cardiff, Wigan, Hull, Burton, Brighton and Wigan are all obvious benefactors. I would also add Leicester and Man City in there.
In respect of other clubs, Doncaster, Rotherham, Colchester, Chesterfield, Derby, Sunderland, Middlesbrough, Arsenal, Millwall, Northampton, Doncaster, Mansfield, Oxford and Shrewsbury are probably where they were before, but in more comfort and more ability to compete.
Huddersfield pre World War 2 were a huge team but fell from grace long before they vacated their Leeds Rd ground so you can't really claim that it was a stadium move that hurt them. They are however now an established Championship club who may even make the Prem next season via the play offs. They wouldn't have done that without a new ground.
Coventry are the victim of an appallingly run club with unbelievably unfit owners. With West Ham it's too early to say as every game for them is an away game almost. It takes 2-3 years to settle into the new home.
We are not a big club. Historically, we should be sitting mid to lower league one. I think FF will give us that ability to make forays into the Championship more likely than they have been through our history.
And whilst mrsblue is correct when she says that new stadia doesn't guarantee success, it certainly does help when attracting players. The only reason we've been able to get the likes of who we have got is down to the stadium dream and a high profile manager like Phil Brown. Without it, we would absolutely have folded by now and end up with our main rivals being clubs like York, Stockport and Southport... if we were still in existence.