I think Centrowitz ran brilliantly to get gold in Rio and is definitely in the discussion to US all time top 1500/miler guy, but his record isn't close to Ovett's, as you suggest.
Ovett won Olympic bronze, beaten by Coe's tremendous kick and Straub's probable doping regime. The Americans being there wouldn't have changed that result.
But he did break WRs at both 1500 and mile, 2 apiece, and was unbeaten over both distances for 45 races and almost 4 seasons. I would be surprised if Centro has won half of his races on the European circuit.
Ovett was also ranked world no. 1 for 3 years and runner up 2 or 3 times. That's 6 seasons where he was ranked higher than Centrowitz's best ranking to date. Of course that might change,
There weren't bi annual world champs in Ovett's day, but he did win 2 World Cup golds against the best on offer at the time, and a European gold.
His accumulated pb'd at 1500 and 1 mile are better than Centro's, and he was competing 35 years ago at his best.
In fact I'd have to put Ovett above Ryun too. He was winning races and medals over a longer period than Ryun.
Centrowitz needs at least 1 No. 1 ranking and a couple of US records to reach Ryun's position. But I bet he's not too bothered, as he has the single most important accolade in any athlete's career.