My favourite times are summer holidays, because although it can be very busy, the main park rides to not close until 11pm ( line entry time ) and I love the electrical parade ( currently Fantillusion ) and the fireworks every night. You do not get this at other times, apart from special dates like Bastille Day and New Years Eve etc. With EMH from 8am and leaving the park around midnight usually, this gives us 16 hours in the park.
When my boys were younger we usually went back to our hotel after lunch to have a swim and relax by the pool until maybe 5pm, then go back into the park for the evening - the Newport Bay Club hotel has the best pools we think. At present, the Disney hotels pools do not open until 3pm, apart from the DLH, so that is a sign of the cutbacks as well.
Now my boys are adult, we like having a day in Paris, which takes 40 mins on the RER line A4 train to Chatelet Les Halles, or a bit longer to CDG Etoile.
We also like going in the beginning of December for low crowds but with all the lovely Christmas decorations and extra events. Fantillusion is on at this time, and also an extra Dreams Of Christmas parade, but no fireworks ( apart from NYE ). The Castle looks amazing when it lights up with dazzling white sparkling lights after the Christmas Tree Lighting Ceremony at 6pm. We like staying in the Sequoia Lodge at this time of year, with the wood/ stone theming and open fire in the lounge.
When my boys were younger, they just wanted to keep on the go and eat fast food when they were hungry, but now we only eat in the buffets or table service restos in the parks, Village or hotels. I think that an all you can eat buffet with loads of choices of starters, mains, desserts, cheeses etc is better value for money than bland fast food which does not really fill you up so you need to buy more later - so in the long run it costs more than the buffet.
January - March ( excluding half term and Easter ) is the cheapest time to go, and usually has good offers like 40% off, free nts / days, kids under 12 free, and sometimes Free Dining, but also when more rides may be closed for maintenance and refurb, and fewer shows and parades, so you don't get an idea of what it is like at other times of the year. I think it lacks atmosphere when it is very quiet, although obviously queue lines are shorter or non existent.
We have visited many various theme parks in this country and abroad, and DLP is no more expensive food wise, apart from America where the cost of everything is cheaper anyway, so cannot be compared with Europe. On our first 3 trips to WDW, staying in the Disney All Stars Movies hotel, our Disney park tickets were included in our package, as they are in DLP, but now you have to buy them separately. By the time you have paid for flights, hotel Disney tickets, tickets for the water parks and other theme parks in Orlando, maybe Busch Gardens in Tampa, Space Centre, money for food, drink and shopping, it is a very expensive holiday, and not possible for some people.
DLP gives them the opportunity to take their kids to Disneyland for a few days when they would otherwise not go at all.
There are also some good rides/ attractions that they do not have in the American parks, and some like BTM, Small World and POTC are better in DLP IMO. The Castle is DLP ( Sleeping Beauty's ) is considered the prettiest one of all the Disney parks.