I was going to recomend MOHAA, but I see you've already played that. Did you know that there is an expansion pack for MOHAA (called Spearhead) due out this month? I am planning to get this, and IMHO MOHAA is one of the best games available at the moment.

I recently bought a re-released game called 'Deperados: Wanted Dead or Alive' (AĴ£9.99 from PCWorld). It's similar to Commandos, but has much better AI, physics, etc.