I could go on with a huge list of recommendations, but I'll just give you my all time favorite movie since it is a rare mention:
Released in 1990, Tremors was probably my first monster movie, followed by Jurassic Park. It follows Val (Kevin Bacon) and Earl (Fred Ward), two working men stuck in a backwater town called Perfection, Nevada. The two finally work up enough money to move away and on their way out they notice that people are dying in seemingly unexplainable ways, and they and the rest of the town have to buckle down and fight the monsters trying to kill them.
It is very much a throwback to the monster movies of the 70s and early 80s, and one of the last of its breed before CG and ridiculous budgets, in my opinion, killed the genre. It uses some damn nice puppets, scale models, and cinema magic to create the effects and remains looking damn good to this day and isn't blighted with the CG issues of its sequels, and is one of the last great examples of a now practically dead form of movie making. This movie is also unique in being one of the few monster/horror movies to take place almost entirely in the day with full desert sunlight.
The movie comes about as close to being perfect as any movie I've ever seen. For the longest time it was my favorite monster movie, but it has since recently graduated to my 1# of all time slot after a few years of re-watching. It is a spectacular dark comedy with great pacing and the main monster reveal is probably one of my favorite scenes in cinema. The cast is amazing and they all work off each other well, even if some only exist to die.
Kevin Bacon and Fred Ward's relationship in the movie is probably my favorite friend duo ever since both bring their A game to the table and deliver some great and funny dialogue, giving a great feel that these people knew each other before the movie started and it gives them some great chemistry. Speaking of chemistry, Kevin Bacon and Finn Carter make two great love interests with just enough pacing and hints to feel natural and deserved by the end. This isn't even mentioning Michael Gross' role as Burt Gummer, who remains one of my favorite monster hunting gunslingers.
The movie spawned a cult following and some sequels, as well as a short lived TV show. If you plan on watching Tremors or already have, I highly recommend Tremors 2 as it is one of my favorite sequels of all time as well. It is more comedy focused than the first and, to be frank, starts to fall apart around the 3/4 mark but overall its still a good movie. Unless you are a hardcore fan, don't bother with 3, 4 and the series after that.
I think the first Tremors is a highly underrated gem and should stand as one of the best monster movies of all time, and if you get any joy out of monster movies I recommend you find Tremors as fast as possible if you have not already.