Learn Hardcore Japanese: otona mo geemu ga suki desu.

“Adults also like games.”
→ For example, maybe you just said 子どもはゲームが好きです (Children like games) and then add 大人もゲームが好きです (Adults like games too).

With the right context, it can also feel like:

“Even adults like games.” (maybe you’re a bit surprised that adults like them as well)

So も marks 大人 as something added to a previous group or expectation: not only that group, but adults too / adults even.

Where is the subject like “I” or “they”? Who is doing the liking?

Japanese often omits pronouns (like I, you, they) when they’re clear from context.

大人もゲームが好きです by itself literally just says:

“Adults also (have-the-property-of) like games.”

It doesn’t specify who is making this statement or whose perspective it is. Depending on context, it could be:

(In general,) adults also like games.
(For us / in our family / in this group,) adults also like games.

If you really want to say “I also, as an adult, like games”, you could say:

私は大人ですが、ゲームも好きです。 – As for me, I’m an adult, and I like games too.
大人ですが、ゲームが好きです。 – I’m an adult, but I like games.

But in natural conversation, Japanese speakers almost always drop 私 / 彼ら / みんな, etc., when it’s obvious.

Why is ゲーム followed by が and not を?

Because 好き is not a verb like “to like”; it is an adjective (a な-adjective) meaning “liked / likable / pleasing.”

The basic pattern in Japanese is:

X が好きです。 → “X is liked / X is pleasing (to someone).”

So:

ゲームが好きです。
literally: “Games are liked / Games are pleasing.”
natural English: “I (or they, etc.) like games.”

If you use を, that usually marks the direct object of a verb, like:

ゲームをします。 – I play games.
ゲームを買います。 – I buy games.

But 好き is an adjective, not an action verb, so the thing you like is marked with が, not を.

Is 好き a verb meaning “to like”?

No. 好き is a な-adjective, not a verb.

Dictionary form: 好きだ
Polite form: 好きです

The structure is:

[Thing] が好きだ / 好きです

So grammatically, “[Thing] is liked / is likeable / is pleasing.”
English expresses this idea with a verb “to like”, but Japanese uses an adjective.

Examples:

音楽が好きです。 – (I) like music.
犬が好きでした。 – (I) liked dogs.
辛い食べ物があまり好きじゃないです。 – (I) don’t really like spicy food.

So, when you want to say “like” in Japanese, you usually use [noun] が好きです rather than a verb.

Does 大人 mean “adult” or “adults”? Is it singular or plural?

Japanese nouns usually don’t mark singular vs. plural. 大人 can mean:

“an adult”
“adults”
“adult people” / “grown-ups”

Context decides which is natural.

In 大人もゲームが好きです, it’s most naturally understood as:

“Adults also like games.” (adults in general)

If you really must emphasize plural, you can say 大人たち, but that often sounds like a specific group of adults, not adults in general:

その国の大人たちもゲームが好きです。 – The adults in that country also like games.

How polite is です here? What’s the difference between 好きです and 好きだ?

です is the polite copula, used in polite / formal speech.

好きです – polite
好きだ – plain / casual

So:

大人もゲームが好きです。
→ Polite. Good for talking to strangers, teachers, in class, on TV, in writing, etc.
大人もゲームが好きだ。
→ Plain. Used with friends, family, or in casual writing (like diaries, manga narration, etc.)

Even more casual, you may see the copula dropped in speech:

大人もゲームが好き。 – Very casual.

Grammatically they all mean the same thing; the difference is politeness level and tone.

What’s the difference between 大人もゲームが好きです and 大人はゲームが好きです?

The key difference is the particle:

は = topic marker, often “as for …”
も = “also / too / even”

大人はゲームが好きです。

Roughly: “As for adults, (they) like games.”
Neutral statement about adults; no “also” or “even” nuance.
Often used when you first introduce the fact about adults.

大人もゲームが好きです。

“Adults also like games.” OR “Even adults like games.”
Implies there is something else already mentioned:
- 子どもはゲームが好きです。大人もゲームが好きです。
  Children like games. Adults like games too.

So も always suggests addition or contrast with something earlier, while は does not.

Can I say something like ゲームが大人も好きです or change the word order?

Not in that simple way; it sounds unnatural.

Japanese word order is more flexible than English, but not completely free. Particles (は, が, を, も, etc.) mark each word’s role, but there is still a preferred order.

For this kind of sentence, the natural orders are:

大人もゲームが好きです。 (most natural)
ゲームが好きです。大人も。 (possible in speech for emphasis: “Games are liked. By adults too.”)

But ゲームが大人も好きです is not normal, because:

も attaches to what is being added (here, 大人), and
It’s usually placed right after that noun, before the rest of the clause.

For a beginner, it’s safest to keep:

[Topic/also-thing] は / も + [thing you like] が + 好きです

How do I clearly say “Even adults like games,” with a feeling of surprise?

Often も by itself can already carry an “even” nuance, depending on context and tone:

えっ、大人もゲームが好きなんですか。
– Oh, even adults like games?

If you really want to emphasize the surprising or unexpected part, you can add words like まで or phrase it differently:

大人でさえゲームが好きです。 – Even adults like games.
大人までもゲームが好きです。 – Even adults like games. (strong “even” nuance)

But in many everyday situations, simple 大人もゲームが好きです can be understood as “Even adults like games” if that fits the context.

Why are there spaces between the words? I thought Japanese is written without spaces.

You’re right: normal Japanese writing does not use spaces between words. It would usually be written as:

大人もゲームが好きです。

In teaching materials, especially for beginners, spaces are sometimes added to:

help you identify word boundaries (大人 / も / ゲーム / が / 好き / です),
make it easier to match words to vocabulary lists.

So the spaces are a learning aid, not standard Japanese orthography.