CNT Raman ratio of G band to 2D band?
I think there might be a mistake in your question...
Around $\pu{2680 cm-1}$, there is the $S_1$ band (attributed to overtone or combination scattering). I think the $2D$ band you are referring to is the band shouldering the $G$ band (also called $D'$) which is around $\pu{1680 cm-1}$.
About the ratio, there are two ratios that are often used to characterise $\mathrm{sp^2}$ carbon based materials such as the CNT.
$$\text{Intensity ratio} =  R_1 = \frac{I(G)}{I(D)}$$
$$\text{Area ratio} = R_2 = \frac{A(G)}{A(G)+A(D)+A(D')}$$
Both these ratios help characterise the degree of organization of your sample.
For more information or more details, I would recommend checking out Spectrochim. Acta, Part A 2003, 59 (10), 2267–2276