Camry has a 192 HP V6. ES300 has a 210 HP version of the same engine
Camry is more mainstream. ES300 is more luxury oriented
Camry has fake wood trim (when appropriately optioned). ES300 has real wood.
Camry has standard suspension tuning. ES300 has 3-position ride adjustment for suspension (at least the previous generation did).
Camry has relatively "tame" standard and optional features. ES300 has lots of cool gadgets and luxury items.
Camry uses "regular" leather. ES300 uses higher grade cow hide, and has those illuminescent gauges.
Camry looks somewhat normal. ES300 has a funky new style to it.
Basically, the ES300 is an Camry dressed up for the prom.