Well the PS3 is BC with PS1 & PS2 if it's a phatty PS3, so if including BC I'd choose OG PS3 (phat) as the best.
For me though it's more about what innovations PS1, 2, & 3 brought not just technologically, but also in driving change to market dynamics, opening up the market, being the center for a lot of console gaming experiences from AAA to AA to indie, and having very distinct brand identities where the console was always front and center.
PS4 still retained a good majority of that and also fixed some business-related issues with PS3. PS5 I feel, has been gradually losing on a lot of those fronts as the gen has proceeded and it's a 50/50 as to if things will course-correct & improve or if the decline in these various metrics continues.