Sure, it's useable in the game industry depending on the project's needs and vision. While listening to several of your cues I heard things that could be improved upon but your questions is pretty hard to answer. Why? Because there are some games that purposely (and successfuly) do what isn't expected. Some things to consider:

- many of the cues I listened to were over several minutes long. This is great for certain types of games and platforms but for some devices this would be too much content. Mobile games, while becoming more and more powerful each year, usually have a fairly small audio data budget. Most of those games want a shorter, looping segment. Writing shorter cues requires a different set up skills and approaches because you need to get right to the point, make it loopable but enjoyable over a long period of time.

- many mobile devices don't have super awesome speakers. Sure a player can plug in headphones but if someone doesn't then you're stuck with the native speaker. Most have little to no low end - due to the small size and composition of the speaker. You need to allot for this limitation.

- you have some interesting ideas and approaches! The biggest thing you need to work on is your actual sounds. They're fighting you because the quality isn't that great. Look into 3rd sample libraries from various companies such as East West, 8dio, Soundiron, Spitfire, VSL, Vir2 and others. Some can get quite expensive but the added realism and flexibility really helps.

- explore more post production tricks and approaches. Even with the samples you have now I think there are many ways you can bring your pieces more to life. Several of the cues I checked out were orchestral so in that vein we're after realism - are we not? You want to be able to convince the listener that an actual ensemble of players performed this piece. This means tweaking things such as tempo, note playment, velocity of notes, volume automation, etc. Do everything you can to make the piece sound as organic as possible. Humans rarely, if ever, play 10 notes exactly the same. Heck they probably don't even play 5 notes exactly the same.

But do companies hire someone just for trailer? Or do they have in-house composers for all this kind of work?
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It varies, really. Sometimes cues from the actual project are used but more often library cues are licensed out for a trailer. There are some cases where an in-house composer writes some music for a trailer. I did that a lot while working for FUNimation.

I love your music
Sounds a lot like film music

-Caleb