I would consider Capello a great coach but not 1 of the best, sure his achievements in Serie A are impressive and he led 4 different teams to win the league title (including Real Madrid). But in Europe, he failed miserably due to his "negative" approach last season. Juz look at how an injury-hit Liverpool managed to get us 2 goals juz at the 1st half in the 1st leg of the quarter finals of the CL and we failed to create anything decent after that, resulting to playing long balls over a team which uses this tactic the most. And in the return home game, he "too calm" and nobody seems to be in a hurry in scoring, and with that game play, I would rather we exit at this stage. However he did bring teams trophies like league titles, even though he will still want another CL title under his name.
Mourinho is indeed 1 of the best coaches ard, and don't let his cocky attitude hinder ur judgement. He manages Porto, an unknown club in the past and guides them to win the league Cup, the UEFA Cup and the CL Cup. It's hard to guide a team that has limited resources to win so much. And his approach to EPL is the "Mourinho-style", which brings them the League Cup.
Benitez is also an outstanding coach, in 2001 he joined Valencia and he led them to win the league title. The same could be said for the 2003/2004 season, where Valencia not only won the League Title, they also won the UEFA Cup. In the 2004/2005 season, Liverpool won the CL under Benitez when everybody thought that Liverpool would be knocked out. But they managed to play on till the end. However his EPL approcah still leaves me a "?"
So I would say that I would group Benitez + Mourinho as the best coaches in the world. Lippi's contributions to Juventus are also remarkable, however we managed to get through to the final CL stage a couple of times and failing to win it, so Lippi ought to be creditted as well. However both Lippi and Capello still leave a big "?" in my mind. For the present team, I would prefer Capello for the job. Lippi is doing reasonably ok in the World Cup Qualifiers since he is still deciding who r the best players to fit his team best, especially the RB position. If Capello is mentioned, some credit ought to go to Lippi as well.