Ljubicic had wins over Federer, Djokovic, Murray, a TMS beating Nadal and Roddick, and a GS semi final which is better than Boredo's cheat-assisted TMS and his bend over jobs in quarter finals. He also defeated Agassi, Roddick, Nalbandian and Davydenko over best of 5 in the same Davis Cup campaign.
Boredo doesn't touch Legenda.
This. Peak Ljubicic is better than Robredo by far and superior to Ferrer too.
He led Croatia to a Davis Cup title with Ancic playing his 2 singles and the doubles too. He could've won more if he wasn't playing with Federer in his prime.
Ferrer isn't a threat to the TOP 4. He does challenge Murray when they play. He beat him at RG last year and almost gets 2-0 in Wimbledon, but against the other 3 is awful. Never beat Federer and lately he's been horrible against Nadal and Djokovic (In 2007 he beat them a few times, but since then...)
For the moment he deserves the TOP 4 since he beats the ones under him and Berdych and Tsonga are very inconsistent, but as soon as Delpo steps up his game a bit he will be the N5. I expect this to be happening at the end of this year.