Imaro
Legend
I agree that 4e combat plays differently from earlier editions, but I don't think you can make the comparison just in terms of hit points/abilities.
4e combat is specifically designed to have a certain pacing/rhythm - the monsters, with their generally greater hit points and more straightforward damage-dealing abilities start out on top, but then the PCs, with their deeper resources to draw on (healing surges able to be accessed in various ways, action points, encounter/daily powers etc) turn the tables and eventually win the fight. In the course of drawing on these deeper resources, the players typically have to engage in a more complex way with the game's action economy (complex triggered actions, subtle options for movement and minors, etc) and work together as a team.
At least in my experience, just playing AD&D or 3E at 5th level won't deliver these particular features of 4e play and a 4e PC.
Personally, I think this has way more to do with how an encounter is designed by the DM... rather than anything inherent in the game system. Perhaps, for you, it's just easier to accomplish good encounter design with 4e as opposed to previous editions... for others that may not be true.