1. I agree that Fritz Reiner's CSO recording is one of the very best.
2. My first experience with Respighi's The Pines of Rome was when I attended a live concert given by The Philadelphia Orchestra in 1984, with Riccardo Muti conducting. Afterwards, I bought their EMI recording, & still enjoy it from time to time. The playing of The Philadelphia Orchestra is worth the price of admission, as they were well suited to Respighi's music in those days. Indeed Muti's recording used to get spoken about as being one of the best in the catalogue, but surprisingly no one has mentioned it here. Perhaps people now think that it has been surpassed by other digital era recordings? such as Charles Dutoit's recording in Montreal?
Personally, I prefer Muti to Dutoit here; although Dutoit and his virtuosic Montreal orchestra do allow the listener to hear the whole score in greater detail than Muti does, which counts for something. While Muti's performance is a more visceral experience,
--The Philadelphia Orchestra, Riccardo Muti
3. In recent years, I bought conductor John Neschling's survey of Respighi's orchestral works with the Orchestre Philharmonique Royal de Liege and the SĂŁo Paulo Symphony Orchestra on the BIS label, which I've enjoyed very much as well, and the BIS recording quality is first class! Yes, The Pines of Rome isn't the only Resphigi work that is worth getting to know--for starters, I agree that The Fountains of Rome is worth hearing too, along with other works. This set makes a good introduction; even though I wouldn't claim that all the performances are necessarily top picks, but they are very good:
4. Another audiophile recording is Eiji Oue's recording on Prof. Johnson's Reference Recordings label with the Minnesota Orchestra, which I expect has the best sound quality you're going to find, and that does count for something when we're speaking about the orchestral splendor of Resphigi's music. & yes, you get to hear every little detail in this exceptional recording,
5. There's also an excellent analogue recording by Lorin Maazel and The Cleveland Orchestra from 1976, which is available on Decca Legends, & comes coupled with Resphigi's Feste romane,
Respighi: Pines of Rome: The Pines of Villa Borghese (I pini di Villa Borghese)
Finally, here are several more Respighi recordings that are recommendable; that is, if you don't wish to buy Neschling's BIS survey, or even if you do--depending on how avidly you wish to add Respighi recordings to your collection:
6. Respighi: Church Windows, P. 150; Brazilian Impressions, P. 153 & Roman Festivals, P. 157 - Cincinnati Symphony Orchestra · Jesús López Cobos, Telarc digital (which is part of another good & well recorded Resphigi orchestral series):
Respighi: Church Windows, P. 150: I. The Flight into Egypt
7. Respighi: Ancient Airs And Dances, Los Angeles Chamber Orchestra, Sir Neville Marriner
Respighi: I. Il Conte Orlando: Balletto (Simone Molinaro)
Or,
8. Respighi: Ancient Airs and Dances & Trittico botticelliano - Orchestre de Chambre de Lausanne, JesĂşs LĂłpez Cobos, Telarc digital
Respighi: Ancient Airs and Dances, Suite No. 1, P 109: I. Balletto detto "Il Conte Orlando"
Hope that helps.