The first major chain to develop a vegeburger, funnily enough, was the Wimpey, with their spicy beanburger, and I absolutely loved it. A real treat. Burger King, to their credit, followed suit shortly after, with a very similar burger, except it wasn't in a round bun it was in a torpedo shaped bun. Nevertheless I was very keen on it and I still sometimes buy them today if I am at a train station, Paddington for instance. It's a bit pappy and the cheese is weird, but it's not a bad product. Mcdonalds, strangely, have never developed a serious vege alternative.
As for the 'gourmet' options. GBK has always put in the most effort and thought. They always have at least three options. You can also choose any other burger and swap the meat patty for a bean patty which I think is a good common sense thing to do. The only slightly disappointing thing is they take things off the menu and replace them with new ones. The best one they ever did was called Billy the Kid and it featured aubergine and deep fried goats cheese. The latest one is a trendy jackfruit offering which I'm unconvinced by. I do appreciate and value their commitment to the vegetarian consumer however.
Byron is cancelled and has been for some time now but before that they were insulting anyway, providing vegetarians with a mushroom in a bread roll that could be eaten in two mouthfuls, absolute pisstake.
Bleeker Burger I first had many years ago when they just had market stalls. I was working on the same market doing coffee and the owner, an American woman, gave me one for free. I really rated it. It does something totally different from everyone else. Just a slab of tofu, a slice of American cheese, some hot sauce and a lettuce leaf. Sounds disappointing but actually is delicious. I like it a lot. Sometimes simplicity is best.
Five Guys don't have a serious vege offering. And their chips are shit. So over salted you feel you are guna die. Fuck them tbh.
Shake Shack on the other hand I like a lot. Their cheesy fries are a bit weird but the burger is great. It's a mushroom like the Byron one but it's been deep fried with gooey weird cheese encased in a breadcrumb shell. The bun is really artificial and weird in a good way. Nothing like actual bread. The lettuce leaf is always very handsome and you get a slice of tomato. I'm a real fan of this vegeburger.