Best vegetarian food is Indian food. There's a place in Indianapolis called Spice Nation that's all you can eat. I go whenever I'm in town.
We don't have "all you can eat" places. At least I have never seen one. I have seen those in US. Food quality is shit, so I avoid. Quality over quantity keeps you healthy.
There's varying quality. I've found that restaurant quality/price ratio heavily depends on taxes and regulatory pressure. Also in bigger cities like Chicago there's restaurant cartels.