Yes, the jokes are good, but without research, I'd be willing to bet that they weren't even Jay Leno monologue jokes.
If you read Wikipedia, Jay Leno announced his retirement in 2004, during the Dubya Presidency.
https://en.wikipedia.org/wiki/2010_Tonight_Show_conflict
When O’Brien’s contract neared its end and he was courted by other networks in 2001, NBC extended his contract and guaranteed him he would be the fifth host of The Tonight Show. The network neglected to let Leno know this until his contract extension in 2004, when they informed him he would remain host for five more years and then transition the show to O’Brien in 2009. When that time arrived, other networks conveyed interest in Leno; NBC, in an effort to keep both of its late-night stars, offered Leno a nightly primetime show before the local news and O’Brien’s Tonight Show.
The Tonight Show with Conan O’Brien and The Jay Leno Show failed to attract immediate viewers, and NBC affiliates, seeing their viewership decline, grew restless. NBCUniversal CEO Jeff Zucker, alongside chairman Jeff Gaspin and executive Rick Ludwin, created a remedy: move Leno back to his 11:35 pm start time and bump O’Brien a half-hour later, to 12:05 am. O’Brien and his staff were both disappointed and furious; when it became clear O’Brien would not agree to the proposed changes, the situation grew heated. Though not a breach of either host’s contract, the change resulted in a public outcry and public demonstrations largely in support of O’Brien.
I don’t recall him ever telling an Obama joke. He told an occasional joke which featured Obama, but never one where the joke was pointed at him. I must have quit watching too soon.
In his later years, his monologue got quite trite and expected until his writers went on strike. He was funny until they came back.