I have been reviewing a lot of my old Japanese lessons as of late and I find that I keep thinking there were words used to express gratitude beyond a simple thank you. I recall ありがとう and the more polite どうもありがとうございます/した. But I keep wondering. When trying to express deep gratitude to someone in Japanese, are there any other words or way to say it? Adding たくさん to it just doesn't sound right to me.
I've seen 申し訳ございません used as well as 申し訳ありません in the same situation. Is the ございません just a more formal way to say it or does it express a deeper gratitude? Or as always in Japanese does it depend on the situation?
ございません is the honorific of ありません, so it sounds more polite/respectful. Speaking strictly, 申し訳ございません is grammatically wrong, but it's widely used and accepted nowadays.