Hawk was the module that really hooked me into the DCS. I did fly A-10C previously, but it is so much heavier stuff to learn, that it kind of held back the joy of flying while learning.
Hawk is a simple plane, easily learned and very fun to fly. Delivering (for me) just the right amount of complexity for the enjoyable learning process. Problem is, it's quite bugged and missing some features right now in 1.5 beta (Works quite well in 1.2), but developer is active and I'd expect it to be in working order soon enough. Also other trainer jets have been introduced recently, I'd see them as very solid starting point for DCS, but don't have first hand experience about them yet.
Also, if you've missed a few years of PC gaming, you seriously need to check out head tracking. I kind of dismissed it way too long for nice but not mandatory gear outside multiplayer. Biggest mistake I've made in a while. It indeed brings the simulation to life and I'd suggest getting TrackIR 5 as soon as possible.