Currently, Thornton is better than Ovechkin, but in the future Ovechkin's goal scoring could give him a slight edge. Toivonen is good, but not as proven as Luongo. Also, Comrie is a 60 point center (which is mediocre for centers), while a healthy Svatos (I don't think he'll be injury prone his entire career) is a 60+ point RW (which is pretty good for RWs) who has a nack for clutch goals.
i wouldnt make the original trade but i would try to work something out. find out if its thornton or luongo he really wants and work something out. if you cut svatos and comrie from the deal and he gives you a 5-10 draft pick i would do it.