Obama only looks better than Biden from a right-wing hack perspective that prefers a mediocre liberal to a competent one, because from their perspective, the former will do less damage. Same reason basically anyone left of center would prefer Ford over Reagan despite Reagan obviously being a more accomplished president by any metric. But from either a left-wing ideological perspective or an ideologically-neutral "how effective was this president at advancing his agenda" perspective, Biden utterly clears. Bar's not very high in either case - we're comparing him to a particularly mediocre president, but he clears it nonetheless
This is becoming increasingly less and less obvious as things go on, and once Trump EO's everything away just like he did to Obama, it's the drawing board again.
He may have the administrative advantage, but he's a terrible figurehead, which is important in convincing the public not to vote to undo, which makes governance far easier.
Also, Obama had a free range McConnell to f*%k over everything, Biden's got an older one, being resisted by Trump.