The Eagles were and have always been bigger in the US than the UK and while, yes, and while their greatest hits is among the highest selling albums off all time worldwide it is nowhere near being the bestseller of all time in the UK. The top three albums in UK sales are "Queen's Greatest Hits", "Sgt. Pepper", and then "(What's the Story) Morning Glory?".
Worldwide it gets beat by "Back In Black", "Bat Out Of Hell", and "Dark Side Of The Moon" for sure before they all get royally tromped upon by "Thriller", the high selling album ever by more than twice "Back In Black"'s (the second highest selling album of all time) sales.
The Beatles and Elvis occupy the two highest selling spots, yes. Zep however has been officially outsold by the likes of Queen, ABBA, Michael Jackson, Elton John, The Bee Gees, AC/DC, and The Rolling Stones. Bob Dylan has sold something like...70 million albums over his career but while that is quite an accomplishment, in terms of sales he doesn't crack the top 80.