Something like a halberd or poleaxe you could also slash with, I suppose, but at that point you're essentially just using a two handed axe, and we already have those in the game.
No...at that point you have an axe/hammer/pointy edge combo on a stick...which is far more exciting than using a simple two handed axe. It also has quite a bit of versatility and range. You can break a shield (usually made of wood) with the axe part, you can then either use the sharp pointy bit to puncture the armor, or you can use the hammer to crush the armor.Using the axe at that point would just be silly as it would just...glance off...
Polearms were the weapons of the rank and file. They were easy to train in, cheap to make, and effective when used in unit-based combat. But pretty much everyone--yes, Vikings included, sir--carried a secondary shorter weapon for when they had to tangle hand-to-hand. A dagger, arming sword, hatchet, or a club of some sort.
Erg, went off on a tangent there. In short, polearms are kinda boring, they're weapons of the lower-classes because they're cheap and easy to make and use, and the number of neat attack maneuvers you could make with one in a game like Dragon Age (which features a number of almost wuxia-like maneuvers) are very limited, unless you get into slashing polearms like Glaives and Poleaxes, which are basically two handed axes or swords. Spears, specifically, would be incredibly boring.
Yes, polearms were used by peasants...and by dismounted knights. If you're fighting mounted enemies you have a greater chance of living if you have a polearm. Ignoring the whole mounted issue, the other point in having a polearm is to have an advantage over those silly enemies that insist on carrying shorter weapons. This is of course ignoring a whole other class of polearms, the polehammers (war hammers). A multi-pronged hammer on a stick is far more terrifying than a five foot sword, and there's a reason the bec de corbin/lucerne hammer was used a lot by dismounted knights/men at arms, and it isn't because they were easy to make/be trained to use. Polearms were quite popular during the middle to late middle age for both "peasants" and more trained warriors.
On a side note, of course they carried shorter weapons with them, they were back up weapons, or main weapons depending on the period. When armor becomes more advanced two-handed weaponry becomes more practical.
Also, whoever said the Gladius was a flexible weapon is just plain wrong. Without the unit of a Roman legion, the gladius was a useless weapon and was utterly terrible for one-on-one combat. The gladius was useless as a defensive weapon, and required the security of the tower shield and shieldwall formation of the legions to remain an effective weapon. It was good for a very particular technique of attack that was not pretty, but was extremely effective, essentially a rotating top-down slash. No fancy parries, no nimble dodges. Just trudge forward and slash, keep your shield high and defend the guy next to you. It was a hoplite formation adapted to a very short sword.
The gladius was also short as much by necessity as design. Bronze is soft and brittle, meaning it could snap easily if the blade made with it is too long and doesn't have a strong spine. Iron and low-grade steel that was also commonly used at the time was also brittle, but worse it was extremely heavy. The earliest broadswords were extremely blade-heavy and required a huge amount of strength to wield, and were useless when parrying. It wasn't until better forging techniques were developed that we saw swords as we know them today, as the flexible weapon as adept at defensive maneuvering as they were at attack.
If the gladius wasn't a useful weapon on it's own the Roman's wouldn't have continued to use it. Legionnaires would be trained to fight using a gladius with/without a shield. They may not have been as effective without the shield, but they definitely could fight without it. The Roman's didn't just slash with a gladius they STABBED too. It is far more effective to stab lightly armored enemies than it is to just slash at them, and that's even more important if you're fighting enemies that wear chain mail. The Romans preferred to stab an enemy in the stomach since it either killed the enemy outright or incapacitated them (where they would then painfully bleed to death). We also have to remember that the Romans carried two pilums with them which were thrown before they clashed with the enemy. The pilums would either kill an enemy outright, or disable the enemies shield to place them at even more of a disadvantage to the stabbing machine that was a Roman legion.
And that's all I have when I'm extremely tired. Ideally it was coherent enough to be understood.
We also have to remember that the Roman's flourished during the IRON age. Yes, that's right the IRON age...where they used IRON (steel) instead of bronze which was used primarily during the BRONZE age. As such, the Roman gladius was made of steel, it may not be the steel that we now use, but it's steel none the less. The Greeks used bronze.