Vanilla WoW gave us two huge continents, eventually 9 -man instances tuned for max lvl (including some massive ones, such as BRD with it´s 18 bosses - would easily be 4 or 5-wing instance by todays standards).
It also carried no less then 6 major raid instances, in addition to world bosses and Onyxia-style short encounters.
Burning Crusade offered a sizeable continent of 8 quest areas, a new major city, and no less then 14 max lvl instances on release, with a 15th eventually added. BC again offered 6 major raids instances to explore, not even counting short encounters such as Gruul or Magtheridon.
WoTLK gave us Northrend, a massive new continent of 10 areas, a new city and no less then 16 five-mans instances that could be enjoyed at heroic mode, (despite these heroic modes being rather undertuned). Admittably, WotLK was a major dissapointment in terms of raid instances, offering only 2 true raid instances (Ulduar and Icecrown) compared to the 6 of Vanilla (ZG, Molten Core, Blackwing Lair, Ruins and Temple of AQ, Naxx) and the 6 of BC (Kara, Tempest Keep, SSC, Black Temple, ZA and Sunwell).
Cata comes with a grand total of... five new questing areas for max lvl players, and seven instances?
There are more relevant instances you can run by lvl 30 then at lvl 85.
Dudes, where is the other half of my expantion content?
(I have enough alts by now, thank you)