"Spartans have two HP. And they can slaughter silver shields pikes if they don';t ven go into a Phalanx Battle and flank. Charging with Spartans is actually pretty good. I wouldn't be stupid enough to impale my guys into a Pike Phalanx."
I'm fairly certain Spartan's have the most powerful charge in the game. As a note, it's better than Cataphracts at least. No mount bonus though so the numbers are deceptive though, still, it is a powerful charge.
For Selucids I would say they're not the best race, nor are they bad. They have the core units of many races, this is true, what they lack is specialist units, 'elite elite' infantry, and mid-range cavalry. And of course archers. They have across-the-board talents but they don't reach the same heights as focused civs.
They have amazing infantry but nothing to compete with the likes of Bezerks, Chosen Axemen, Elite Cohorts and Spartan Hoplites. They lack specialist units such as Night Raiders, War Dogs, Gladiators, etc.
Their cavalry are good but setting aside Greek Cavalry and Militia Cavalry (both rubbish) they have two choices: Heavy or Superheavy. No light, fast horse archers or AP swarmers like Head Hunters or Desert Cav, no specialist cav like Camel Lancers or Cataphract Camels. No solid mid-range cav like Long Sheilds or Macedonian Cavalry.
On the campaign map they suffer further as they can't get any good temple upgrades. Hephastus is nice, but nothing like the Macedonians (Artemis and Ares) or the Greeks (Nike) etc. Which only serves to increase the 'good at everything but awesome at nothing,' gap.