Rijkaard who is a CL winning manager had the same players plus a few more and got nowhere close to achieving what Pep did at Barca. City coaches have had blank checques for a decade and didn't achieve what he has. The only club this statement is true is at Bayern.
In 2008-09 when Guardiola arrived, Madrid had a 31 year old Raul and a young 21 year old Higuan as their top scorers with 24 a piece. 32 year old Nistelrooy was the next highest scorer with 10.
If you look also at the rest of the squad, you'll see Madrid were in a period of transistion.
On the other hand, in 07-08 Barca were well underway in their reconstruction before Pep had even been made the manager. In came Henry, Yaya Toure and Abidal as notable incomings.
Messi had been in the team for 4 years, but from the age of 16 and his goals were 1,8,17 then 16. Now you might credit Guardiola for Messi hitting 38, 47,53 and 73 in his following 4 years, or you could say Messi had reached maturity.
Take into account Henry who Rijkaard brought in got 26 goals and Eto'o 36. Even Xavi and Bojan got 10. Again you could credit Guardiola, but the truth is he had an embarrassment of riches and were against a transitioning Madrid.
Guardiola also got significant reinforcements in his first summer which quite reasonably may have had very little to do with him....including Kieta, Pique, Alves, Hleb.
Busquets was promoted from Barca B so maybe he can take some credit for that. In 08-09 he also promoted Pedro who turned out to be very good so maybe credit also due there.
Madrid in 11-12 still arguably in transition managed to take the title and Barca only won the domestic cup and thats still with Messi scoring 73 goals in total that season.
City won the title in 11-12 and 13-14 and were 2nd in 12-13 and 14-15 so to say the blank cheques achieved nothing is very incorrect.
They had a relatively poor year in 4th in 15-16 which is when Pep arrived. In his first season he got 3rd despite bringing in Gundugan, Nolito, Zinchenko, Sane, Stones, Bravi, Jesus and Moreno. Only outgoings were Demichelis for free, Richard Wright retiring. Dzeko out for £10.8m and Jovetic for £12.2m. A net spend of £144.2m which is still argubaly half what it would be if buying those players now, so Guardiola also had the benefit of a major boost before prices rapidly increased again.
Take into account he inherited Aguero, Sterling, Silva, Toure, Kompany, Zabaleta, Fernando, Kolarov, De Bruyne, Fernandinho, Otamendi, Iheanancho. Many of those costing fortunes.
In 17-18 he also spent another £200m net.
The spend was unprecedented and on top of an incredible base.