At home I make the following regularly
Pasta
Stir fry
Soup
Curry
Casserole
Chilli
So if I'm being offered that when paying it better be good! Being charged £10+ for pasta in a jarred tomato sauce is taking the piss!
Suggestions for a restaurant (and yes depends on restaurant type)
Change seasonally so your veggie guests aren't facing the same options year round (and yes the same courtesy should be offered to the carnivores).
Spring
Good seasonal veg soups
Light good quality pasta dishes
Warm salads with couscous, quinoa, rice base seasonal veg and optional cheese/eggs/nuts/seeds
Summer
Good quality cold salads
Good veggie burger option
Something South American style - tacos, loaded potato skins, Guac, sour cream etc
Autumn
Hearty root veg soups
Chilli
Stir fry
Winter
Roast alternatives (made with nuts, chick peas, lentils, peas, root veg) served with typical but veggie aware accompaniments roast potatoes, yorkies, veg stuffing, veg gravy - also perfect for Christmas do's.
Hearty veg curry well flavoured
Well seasoned casserole with veggie suet dumplings
I happen to like quorn (I know some veggies don't) so restaurants could easily provide veggie versions of meat dishes simply by 'swapping out'. A wetherspoons type place near me does this and it means in there I can get:
A fry up! (Eggs, veggie sausage, veggie bacon, beans, tomatoes, mushrooms, tattie scones)
Veggie burger - with all the same topping options as the meat ones
Hot dogs, Chilli, quorn fillets with same sauces as for chicken/steak dishes etc
I also love shepherd type pies, macaroni cheese, pastry bakes, risotto (but yes not microwave watery crap, and not always mushroom)