I voted for two.......but it really depended on the day. Some days we only did one, some we did 2, and on 2 days we didnt go to the parks at all...........just did downtown disney....
I said 2, but it varied from day to day. ; Generally, we hit one park in the morning, went back to the hotel in time to get some 'free' food (concierge level room) and then went somewhere else for the afternoon. ; In one or two instances, we hit a third park to catch the Extra Magic Hours... but on other days we only hit one place, or just hung out at Downtown Disney. We're not really water park people, either.
Depending on how long we go would matter how many parks we visit a day. ; But we generally spend one day at one park. ; Of course we do get the hopper passes and go to any other park when we want. ; Usually on the last day we go to the ones that I wanted to buy stuff and didn't. ; Makes for a fun day of shopping and trying to remember where I found something.
Usually we do at least 2 parks in a day. Last trip we spent the morning and early afternoon at DHS, back to the Boardwalk for a swim and then off to Epcot for Illuminations. We always buy PH tickets. The next day we had PPP tickets so we lounged around the resort most of the day and hit MK @ 16:00.
On our last trip we only did 1 park per day, but this was very unusual. For the most part we do 2 but have on one occasion have done 3, AK, MK, EPCOT.
Normally we wil do two parks per day. We'll catch the park with Morning magic hour then go to another park in the afternoon. During Mousefest we caught three parks in one day AK, Studios, Epcot was able to do the highlights from those three parks easily.