MMORTS and Online RTS games usually offer considerably more graphics and action than free online strategy games.

MMORTS

Beyond Protocol 
Graphics: Yes
Download: Yes
Free or Pay: Pay
Fight over resources with other players while building your own army, navy, and air force.

 

Boundless Planet 
Graphics: Yes
Download: Yes
Free or Pay: Pay but has free trial.
Fight over resources with other players while building your own army, navy, and air force.

 

Project Visitor 
Graphics: Yes
Download: Yes
Free or Pay: Pay
Battle other players in 3D over a new energy source called Transium.

 

Dreamlords - 2008 Online Game Award Winner
Graphics: Yes
Download: Yes
Free or Pay: Free
Combines RPG, RTS, and tactical strategy elements all into one game. 

 

Shattered Galaxy 
Graphics: Yes
Download: Yes
Free or Pay: Free but also has a premium version.
Real time strategy meets MMORPGs in a Science-Fiction world.

 

Picaroon
Graphics: Yes
Download: Yes
Free or Pay: Free
Free MMORTS with a futuristic pirate setting.

 

DarkSpace
Graphics: Yes
Download: Yes
Free or Pay: Pay
Spaceship-to-spaceship combat where players look to gain rank and prestige. 

 

Pay Online RTS and Strategy Games

Warhammer 40,000: Dawn of War
Graphics: Yes
Download: No
Needs to be Bought: Yes
The popular Warhammer franchise in a post-apocalyptic universe.

 

Battle For Middle-Earth II
Graphics: Yes
Download: No
Needs to be Bought: Yes
Improves on the original to be one of the better games in the Lord of the Rings universe. 

 

Artifact - Interview
Graphics: Yes
Download: Yes
Needs to be Bought: No
Build empires using Ancient Artifacts in this real-time strategy MMORPG.

 

Dragonshard
Graphics: Yes
Download: No
Needs to be Bought: Yes
RTS set in the Dungeons and Dragons world known as Eberron.

 

 

StarCraft
Graphics: Yes
Download: No
Needs to be Bought: Yes
Not only one of the best RTS games but also one of the best games of all-time.

 

Warcraft III 
Graphics: Yes
Download: No
Needs to be Bought: Yes
The most recent installment of the vaunted RTS franchise.

 

 

Trash 
Graphics: Yes
Download: Yes
Needs to be Bought: No
Small online RTS set in a post-apocalyptic world that supports up to 24 players simultaneously.