Arsenal's success is build around one man and that is arsene wenger. The guy is not just a great coach. He's the one who decides who to buy and who to sell. The man's record with transfers are "perfect", Better than any manager in Europe in that Dep. (even better than both mourinho and ferguson). Add to that the exciting-attacking football that his team plays (perhaps the main reason behind the growing number of arsenal fans in the world).
A club that depends soo much on one person for its success is in a real trouble once that person leaves. Thats why the owners of Arsenal are doing everything possible to keep Wenger there.
Its true that we depend a lot on Wenger, and its true that he transformed this club into a one of the top clubs in Europe financially, he was behind us getting new state of the art training facilities, and then after that the new stadium and the subsequent sponsorship deals and all that. So all in all, nobody has done for Arsenal as much as Wenger has, and for that all Arsenal fans will forever be grateful.
But, when Wenger leaves Arsenal in a few years, he will leave us in a very good financial state, and i think we can go on without him, as i'm sure whoever comes after him will have the funds required to compete.
Sure, that's easy to say when a manager just focuses on signing young players and develop them, rather than buying expensive/known players he brings in a handful of youngster who he aims to develop, of all those he signs, less than half will actually make it into the squad, let alone break into the first team. Those who don't could be very well considered "flops" as they didn't live up to expectations, which were being capable of being a useful player for the team.
But just to name a few Arsenal flops:
Luis Boa Morte
Christopher Wreh
Silvestre
Baptista
Cygan
Wiltord (taking into account his price)
Van Bronckhorst
Reyes
Kaba Diawara
Francis Jeffers
Richard Wright

lol2

Hleb
Pennant
Oleg Luzhny
Rami Shaaban
Fabianski

shifty
There are many more, so yeah, that's hardly a perfect record. Every team has a lot of flops anyway.
You're being a little harsh here Gabriel, he has bought players that nobody expects are good, and they've turned out to be very good players. A lot of the names you mentioned shouldn't really be there.
Rami Shaaban was a third choice goalie, not a particularly bad one at that either.
Reyes could be considered a flop, but thats only because he didn't really settle in with the culture, the language, the weather etc. He played a lot of good games for us, and actually won the best player of the month award once.
Pennant, we didn't buy.
Hleb i wasn't a big fan of, but he had a couple of good seasons.
Baptista was horrible, but he was just a loan, and he was a last minute one too, one that we had to do because Reyes insisted on leaving in the last days of the transfer window, and that was the best deal we could strike with Real Madrid.