The Blues top the Premiership table while West Ham currently lie fourth.
In a chat with Chelsea FC site, Mourinho feels both teams have impressed since the season began in August.
"I think Chelsea deserve to be top of the League,' said the Blues boss.
"After us, for West Ham to be fourth, for a team that everybody was expecting to be fighting for survival, I think is a fantastic achievement. Really, very good.'
Last season's corresponding fixture saw the Blues frustrated as West Ham, who were struggling at the lower end of the table, defended in large numbers.
"Both teams are different from last season,” Mourinho told Chelsea FC site. "We are a better team, we have more creativity, more goals, more attacking dynamic.
"West Ham are also a better team. They are not just a team who don't want to concede, they also try to score goals, so the game will be very difficult. Both teams have the capacity now to produce a completely different game.
"Last season, they were in big trouble. When you are fighting against relegation you have to do everything to get a point. It was a turning point for them as it gave them the confidence they needed.
"They stayed in the division but this season is different. The way they play every game they are a more complete team, more difficult, a different team with better players and also Big Sam is showing now he's not what people sometimes say.
"They say he's a defensive coach, he only knows how to play physically, direct, long balls, but he is giving a different impression of himself which can make the game more difficult for us, but at the same time more attractive for everyone."