A great addition to the Tiberian Sun saga.Has better mission designs but not as good a story as the first Tiberian Sun.
Kane is dead,NOD have become divided as a power vaccum sweeps through it.One of Kane's former commanders named Slavik stored Kane's ideologies on an AI named CABAL hoping to keep Kane's vision alive.Tiberium is still spreading through the world and deadly mutant lifeforms which can travel fast through the air and can easily kill humans and will do so on sight are emerging.NOD and GDI are still searching for more alien technology.The GDI are still trying to stop NOD and the spread of Tiberium.
A big plot twist happens that I won't spoil for you but to me it seemed like the story for Firestorm begun to stall near the end and went in weird directions due to lack of fresh ideas.
The gameplay is much the same as in the first Tiberian Sun game,except the missions are harder.Even on the easy difficulty level you'll need to think out of the box and utilize different units more than in the first Tiberian Sun game(which is a good thing).The mission designs are done quite well to make missions challenging and to make you be more productive with your unit building/base management and to discourage the tactic of being defensive and then building 30 tanks and storming your enemy base with them.
There is new units and structures of course.However,the new units don't make the factions any more and less balanced really,unless you like using artillery.The new units look impressive and so do their abilities such as he mobile EMP,cyborg reaper,mobile stealth generator but you don't really need to use them to win missions.The best tactic to win missions is to once again build lots of tanks,however you can utilize certain units that were already included in the original Tiberian Sun such as GDI hover tanks to make missions easier but even if you use the ''build 30 tanks and flood your enemy base with them'' strategy,in Firestorm you'll need to be more aggresive in the later missions than you were in the original Tiberian Sun game because you'll need to prevent long-ranged missle strikes or destroy enemy unit producing buildings unless you want to be overwhelmed by numbers or long-ranged missle strikes ;)
However,you'll need to be tactical with your defense otherwise your base can be destroyed by a horrible surprise.
The graphics are quite the same as in the first Tiberian Sun(detailed and sharp looking for their time).I like CABAL's voice and evil laughter,especially when you hear it mid-mission.
Overall-The score I've given this game might seem high but I love the C&C series(with the exception of the Generals games)and I enjoyed playing this game a lot because it continues the Tiberian Sun storyline and it's mission designs make the missions more challenging but satisfying to win.