http://en.wikipedia.org/wiki/Mongol_Empire
"It is commonly referred to as the largest contiguous empire in the history of the world. At its greatest extent it spanned 9,700 km (6,000 mi), covered an area of 24,000,000 km2 (9,300,000 sq mi),[1][2][3][4] 16% of the Earth's total land area, and held sway over a population of 100 million."
I will argue that what the Mongols did is more impressive empire than what the British accomplished. One the Mongols usually faced opponents with similar technology or greater than them. The Mongols had superior tactics. The British mainly just took advantage of natives with superior technology (guns, and awesome ships). The British tactics for the most part not were too impressive. Sure some battles they showed some very cunning tactics but for the most part it was line up and shoot or bring in the cannons. The Mongols however used deception and usually fooled almost all their opponents into thinking they were retreating. They didn't always use this tactic but they used it a decent amount (especially in Europe). Kind of hard to reach your opponent when they are on horse backing up and firing off shots every so often.
Anyways moving off of tactics and onto the actual land of the empires. Did the British control more land? Perhaps but I would argue that controlling a contiguous empire is highly more effective then being spread out all over the globe. What happens when you settle colonies in foreign lands. Eventually the people start associating themselves as an individual nation and not belonging to the motherland due to the long distance relationship. Good examples would be USA and Carthage. Before Carthage become an empire they were a Phoenician founded city. I know this was unnecessary long and drawn out but I will not let you win an argument putting the British ahead of the Mongols. Do the British deserve respect? Yes but the Mongols deserve more in terms of military accomplishments. Besides it is sad that Khan never really lost a battle ever.
Basically, if a Mongolian ever faced a British troop during that time period they would destroy them.
I apologize for the off topic rant and I will self enforce a 10 hour ban on myself.