'expat, does it have to? Would it still be crap if there were a big park nearby? Or woodland where they could make dens? Or do they need their own space, do you think?'
Yes, yes it does have to. Especially until they're old enough to go a park on their own, which means in many cases they need to be quite road savvy if they have to cross any roads.
Make dens in woodlands? LOL.
Otherwise, you get to spend a big part of everyday, on top of everything else you have to do, either going to the park, over and over, or getting nagged to go to the park. In the rain. No chucking them out in the garden to splash. Nope. You gotta go, too.
I'd sell my soul for a garden to have them out in whilst I pegged out the clothes, tended the garden, play a quick game with them rather than long blocks of time traisping to the fucking park, could have a trampoline in, other children over to play in, BBQ/make tea (with kitchen door open) whilst they play, do activities in (like tie-dye, water pistols, giving them pails of coloured water and telling them to paint the house, etc.
It is a fucking nightmare not having a garden, IME.
I'd sell my body for £20 a pop to have a garden. I seriously would.