In this Letter, we study the high frequency dynamics in the glass transition region, and present measurements of the SsQ, vd in three glass forming systems: glycerol (GLY), o-terphenyl (OTP), and n-butyl-benzene (NBB). In all these systems, we find a propagating longitudinal collective dynamics in a temperature range extending from the glass to the liquid phase well above Tg, and up to Q transfers approaching the inverse of the interparticle separation. This result confirms and generalizes previous findings obtained in a molecular liquid as water [5], and in other glasses as SiO2, glycerol, and LiCl:6H2O [6]. Specifically, it shows that this dynamics is the high frequency continuation of the acoustic branch detected with ultrasound and Brillouin light scattering techniques. Moreover, at a given Q, we find that the temperature dependence of the excitation frequency, VsQ, Td, is more pronounced in the liquid than in the glass, and has a cusplike behavior at a temperature Tx which we infer to be higher than Tg. We associate this behavior to the liquid-glass transition at the investigated frequencies, which manifests in a change of the collective dynamics likely to be due to the freezing of the microscopic diffusional processes. The common behavior among the considered systems may lead us to speculate on a more general origin of this property, and