Fourth seed Cilic, victor in 2012, overpowered American teenager Stefan Kozlov 6-0 6-4 while Querrey, who triumphed seven years ago at the west London club, got the better of Australian Jordan Thompson, winning 7-6 (3) 3-6 6-3.
Cilic is the only top five seed left standing at the Aegon Championships after Andy Murray, Stan Wawrinka and Milos Raonic all crashed out earlier in the week.
"He has been playing unbelievable and is also a great grass-court player, so I think I have to play my best tennis if I want to win".
Cilic - the 2012 champion and 2013 runner-up - was supreme on his own serve throughout the match, dropping just four points on his first serve and firing down an impressive 20 aces.
Lopez beat former Wimbledon finalist Berdych in three sets in the Stuttgart quarter-finals last week, and the Spanish world number 32 repeated that success with a marathon 7-6 (7/5), 6-7 (1/7), 7-5 victory lasting two hours and 27 minutes. That match will conclude after the singles final on Sunday. It is one of the tournaments that you, first of all, you love.
The big-serving duo put on a spectacular show for the crowd in London, with Cilic eventually proving too strong as he ran out a 6-3 5-7 6-4 victor.
It took almost nine sets this week for Lopez to lose his serve, helping Dimitrov take the semifinal to a deciding set.
"We had a great battle in the 2014 final so I knew it would be tough", said Lopez, referring to a match that featured three tiebreakers.
A rain delay midway through the second set broke his rhythm though and sixth seed Dimitrov seized his chance to level.
The heart-wrenching defeat to the Croatian ended Muller's grass court winning streak but the Luxembourg player will head to Wimbledon with his head held high after an impressing week on a grass court.
Former champion Marin Cilic is back in the Queen's Club final seeking a second title at the Wimbledon tune-up in London. He has previously won this tournament and lost just seven of his first-service points through three matches en route to the semi-finals, which indicates how well he has been serving.
In the victory, Cilic won 91 percent of his first serve points and 58 percent of his second serve points.
"Today's match was an extremely high level", said Cilic.
"It's hard to believe I'm playing my best tennis at 35, but yes I am", he said.
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