MW4 Mercenaries is just great for the MW Series. It is fun, has great action, a solid story and good sound and visuals.
MW4 Mercenaries has many missions to choose and play, however you cannot play them all as you generally swing more to one side and the other side doesn't offer you contracts anymore. Also, you have specific hard points on a Mech which can only be equipped by certain types of weapons. There are omni hard points on Mechs which enable any type of weapon to be put on (providing that it is large enough to cater for the huge armaments). The weapons are fantastic and the noises they make are impressive. The areas in which the missions take place are great (terrain, atmosphere and location wise).
MW4 Mercenaries has a good sound track to keep you pumped when in action, or when there is no danger. The style of earning money to improve your rank as a mercenary and increase your power and strength is another great thing for the game. Even when you have finished single-player, you can customise a quick mission and choose what Mechs you will have on your team and what Mechs you will be against. There are great areas to choose (single-player missions) and also the Multiplayer is good online. Without Internet, you still have a fantastic game and hours of fun which gets points in my books.
Not only does MW4 Mercenaries have well all round stats, but it also has such list of good characters and voice overs. A favourite voice is the one called 'Duncan Fisher'. When you are about to be attacked it is also great to hear the leader of the enemy talk and your character talk back. When Mechs are hit, or explode or do whatever they do, it looks great and it is satisfying when you take out a Mech which is in mid-air.
MW4 Mercenaries is definitely a great 'Mech Game' because everything that makes a 'Mech Game' good (action, story and designs), MW4 Mercenaries has plus more (choosing what you attack in a custom match, playing campaign maps).