There’s a lot of flavor you get from cooking over fire that you won’t get on a GF. You won’t be able to cook a steak the same way where you create a delicious char on the outside over a very hot grill.
However, I prefer cooking sausages and hot dogs on the GF because I don’t have to deal with the flare ups from the fat dripping on fire. I also think it does a better job of cooking chicken without drying it out.
One trick to cleaning the grill is to clean it while it’s still hot. Use some wet paper towels to wipe the hot grease out and you’ll get it almost perfectly clean.
A George Foreman grill works fine for quickly cooking things like chicken breasts and burgers, but there are a lot of things that won’t even fit on one. Bone-in chicken breasts and whole chickens (or worse, bigger birds like turkeys) do fine on on outdoor grill, as do big chunks of roasting beef (and other meat), and corn on the cobb, but none of these are easy on a foreman grill. You can’t really grill vegetables on it, they don’t cook out the same way. It doesn’t give you the sear or smoke flavor either. You can’t slow cook or smoke on it.
Basically, it’s a handy tool for quickly cooking relatively thin stuff that fits neatly. I like mine a lot, but it’s not remotely a replacement for an actual charcoal or gas grill.