An improvement but still below average in terms of C&C standards
Singleplayer follows the events of the GDI ending of Tiberian Sun. Kane is dead....again... With Nod severely weakened, GDI looks to focus on the Tiberium infection and how to cure Tiberium mutations that have been killing millions. Nod looks to stay strong as they await Kanes return. Whichever side you choose to play, your goal is to eventually revive the Nod AI CABAL. However, CABAL betrays you and begins going on a rampage with his cyborg army. As CABAL gets stronger, Nod and GDI are forced to ally together to take out a superior threat.
Since its an expansion, funding is obviously on a lower budget so no big name Hollywood stars like James Earl Jones or Michael Biehn, but Firestorm continues the tradition of live action in-game cutscenes. The story is interesting, as CABAL becomes the main threat of the storyline.
As mentioned, Firestorm tries to improve on Tiberian Sun's biggest cons. The maps were designed to have more variety so they are more visually impressive. The new units that are added look much better graphically.
The new units also make improvements for the gameplay to be faster. Both sides have Mobile EMPs and Mobile War Factories. While EMP was usually just a defense mechanism in TS due its short range, with the Mobile EMPs combat becomes much more flexible in terms of how to attack. Mobile War Factories also benefit the player for building additional units away from base and closer to the action so they can re-enter combat asap.
GDI also gets a new unit called the Juggernaut, which is GDIs answer to long range firepower vs the Nod Artillery. Like the Nod Artillery, it must deploy before it can start attacking. It can destroy buildings from afar and destroy incoming units before they reach you.
Nod also gets new units such as the Cyborg Reaper. Like most of Nods units, the Reaper is fast and very versatile in terms of mobility. It has a rocket launcher as its main arsenal that can quickly decimate vehicles and a net that immobilize infantry. Nod also gets the Mobile Stealth Generator. Once deployed, it can create a cloaking field much like the structural Stealth Generator, but not as large radius.
Firestorm also makes some balance issues in terms of combat. Nod Artillery had incredibly overpowered splash damage in TS. If the shell would land far away from the targeted unit, it would still deal 100% damage. Its splash damage has been fixed in Firestorm. Also, the GDI Jump Jet Infantry speed was increased. Hardly anyone utilized Jump Jet Infantry in TS because they were incredibly slow and would get shot down before they do any real damage. Their new speed makes their combat value go up and more variety in GDI attacks.
While the improvements in Firestorm were good, improvements on a mediocre game still make it a mediocre game. It definitely has a lot of high points, and the new units do their best to speed up gameplay, but the slow gameplay can't really be addressed unless the game experiences a full reboot.
Firestorm is fun while it lasts. If you are a TS fan, you will like the changes they make in Firestorm.