Unreal Tournament 2015 is UT99 at it's core mixed with a few things from Unreal Championship 1 (which was very different from UT2k3/UT2k4) & 2 as well as a couple things completely new to the franchise as a whole. It has the base model of UT99 minus the ripper (bring it back dammit!) combined with wall jumps (but no double-jumping), wall slides, floor sliding, a dodge system that doesn't require double taps (something that always caused me to fall off maps in previous games) a super clean aesthetic like UC2 that still somehow remains similar to UT99 in terms of realism, and non-placeholder weapons that are essentially newer models of what existed in UC1 (which in turn, were improved UT99 weapons made specifically for competition. Not nerf guns like in UT2k3/UT2k4 or steampunk and Gears-styled contraptions like UT3). There's still hardly any blood or gore, the amount that exist is lower than that of UC2. Sound wise almost everything is UT99 and UT3, only one or two things exist from other UT games in this regard and there's word that the original composers for Unreal/Return To NaPali and UT99 will return, though it should be noted that the main theme sounds like it took more influence from UT2k4's menu remix. Interface layout is virtually identical to Unreal Gold and UT99, just given a modern look.
Toxikk is essentially the spiritual successor to UT2k4, but borrows a lot from more grounded games like Halo for it's weapons. UT2k15 got it's dodge input from this game. It features double jumping and wall jumping just like UT2k4 did, though wall jumping is a lot easier to do this time around. In terms of outdoor gameplay, it will kick the shit out of UT2k4 and UT3. In terms of more traditional arena play, it's going to fall behind it's competition. Aesthetically, it's very detailed and occasionally cluttered like a lot of the Unreal games were, but has a very realistic look to it. Interface is laid out similar to UT2k4.
ECKZBAWKZ HUGE LIST OF ACHIEVEMENTS GOES HERE....
Oh wait.