I think what we miss from our curries is not the "taste" but the "smell"
For me this is absolutely true. And it's why, despite what others may say, I still think there is a missing 'secret' ingredient. That smell has to come from somewhere and it must be from something that we aren't putting in our curries.
This is what curryhouse.co.uk has to say:
"So are fenugreek leaves essential? No, but they do make the standard curries (do-piaza, Madras, dhansak, bhuna etc.) taste like they came from a restaurant. Having said that, no curry house puts them in all their curries. For instance, they taste awful with creamy or yogurty dishes such as tikka masala and korma."
and:
"if (green herby bits)...look a bit like thyme they are probably fenugreek leaves which, in any case, have a very distinctive aroma. They smell like every curry house you've ever walked past in the street."
He's probably right. But if it's so obvious, why is it that we haven't all agreed it's definitely fenugreek, dead simple to replicate at home, problem solved?