The central powers promised Italy a lot of lands and more colonies than the Entente, maybe if looked at from a more rational point of view their offer was actually better, but when you read about the encounters that the Italian foreign minister made with ambassadors from both factions it is clear that Italy only really cared about Trento (a city in Tyrol) and Trieste (a city in Istria).

Those cities and the nearby regions were considered what separated Italy from completing national unification, it was taught in the schools and engraved in the minds of the citizens: Italy one day shall go to war against the Austrian oppressor and unify once and for all.

It was just too important, nothing that the central powers could have offered would have changed Italy's mind and the shared hatred between Italy and Austria-Hungary didn't make talks easier.