The N-Gage-compatible Nokia N79 has been reviewed over on All About Symbian, so if you're interested in this phone head on over to see what they think of it. It's been touted as a replacement for the N78, but it has higher tech specs and a higher price to go with them.
The N97 does indeed look pretty exciting, but it's a long way away (estimated release is in Summer 2009). The only models available now are pre-production prototypes with non-final firmware, and they don't have the N-Gage client on it yet so it's difficult to judge what it will mean.
The d-pad should (hopefully) be good for games, and the keyboard will allow plenty of room for customising controls though the buttons themselves may be a bit small.
Screen resolution is a mixed blessing: a bigger screen is always nice, but it slows down rendering of 3D graphics even on devices with hardware graphics chips. For example the E90 renders 3D games much more smoothly on its smaller exterior screen than its much larger interior screen.