The new X2 7750 is definitely better
than the X2 6000+ for gaming (and other apps, whole article is worth a read). It even stacks up pretty well against the e5200 in many uses (at stock speeds, that is).
Basically they took K10 (Phenom) and stripped it down to two functional cores instead of trying to tweak more performance out of the older K8 (original X2) architecture. K10-based Phenom X4 can best a low cache C2Q (Q8200) in some cases, especially when the clockspeed difference is significant (stock Q8200 vs X4 9950 for example). So it's not too surprising to see the K10 X2 chips competing with the low-cache C2D chips.
EDIT: You might want to keep the power consumption
in mind also. Read some of the reviews at newegg, many people are complaining about the heat generated by these chips and saying that stock cooling just isn't doing the job.