As noted, the G dailies require high level, at least partially awakened teams to beat. I've cleared them all save the trust item G map (as I've not bothered attempting it yet), and will note that in most cases it can be worth it.

The Monday G daily is the best map for Plat Armors, having the highest drop rate and two possible drops for them. It is however worse than the X map for gold.

The Tuesday/Friday map is arguably the best map for black spirits, having a 30% drop rate (the same as Dwarfs and Giants Challenge map), along with three chances for them to drop, however while it only costs twice the stamina of Dwarfs and Giants, it costs a large amount of charisma, so some may argue it is not worth it just for the black spirits, it also has good drop rates for Platinum spirits (with two chances), and the best drop rate for rainbow spirits (with two chances) compared to stamina spent (unless you have the spirit drop rate boosting bandit, in which case the E difficulty is the most efficient for Rainbow spirits, I forget off hand if that is only if she's awakened or not though).

Wednesday Gs are from what I recall both the best rates for gifts, but I generally don't find them worth it (mind I don't tend to find the gift dailies worth it in general) since I find saving my stamina for Thursday more valuable, and get more than enough gifts doing challenge maps on the weekends and occasionally from events, if I was in dire need of gifts however, they would likely be the most efficient way to from them (such as if we had constant back to back events).

Thursday G map is the best of the demon crystal maps hands down, with the best drop rate, the same stamina cost as the H and X versions, and one more possible drop than the H version (same as the X). It also has a 100% drop rate when the 1.5 times drop rate for daily missions events occur.

Overall, the G maps are usually better than the lower difficulties, but may be worse at a specific aspect. Overall, it is dependant on what you are going for.