Take a look at the features of Celtic Kings.
Take a look at the features of Punic Wars / Nemesis of the Roman Empire / Imperivm II.

New features

• Completely new nations of Britons, Egyptians and Germans each of them with its unique gameplay style, units and upgrades
• Separation of the Roman civilization into Republican Rome and Imperial Rome.
• New single player modes - Great Battles of Rome, Great Challenges of Rome and Conquest of Europe.
• New combat system. Addition of 'Stamina' statistic used by units for using their specials.
• New unit specials including Triple strike (the unit deals three times her usual damage), Drain (reduces target's stamina by 2 on a successful attack), Expertise (instantly kills an enemy if unit damage is increased after adjustments with enemy armor and level modifier).
• Additional hero skills. Now each hero has an addition of six skills which benefit as well as him as his army. Five of the skills could be developed.
• Completely redone walls. Now the walls of players' strongholds are guarded by sentries who are able to shoot down every enemy.
• New items including Scroll of Dead (every attached warrior has a 10% chance upon death to transform into a Ghoul), Amulet of Triumph (heals the bearer by 100 every time he kills an enemy), Elephant Tusk (heals the bearer by 20 every second).
• New custom maps
• A lot of new graphic effects.
• New music and more than 100 new sound effects.
• Dozens of additions to the CK and PW engine: new outposts, improved naval battles, improved help system, etc.