A detailed comparison of the solubility of carbon dioxide (CO2) and methane (CH4) in ionic liquids (ILs) and in conventional solvents like Selexol, Purisol, propylene carbonate, and sulfolane is presented. The solubilities are compared on mole fraction, molality, and volume basis to demonstrate the effect caused by the high molecular weight of ILs. We found that conventional solvents are superior to existing ILs in terms of mass- or volume-based solubilities. Monte Carlo simulations have been used to quantitatively predict the solubility of CO2, CH4, and C2H6 in the solvents 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [hmim][Tf2N] and tetraethylene glycol dimethyl ether.