Mér fannst brokkolíið betra í dag en í gær.

Because the verb finnast uses a dative experiencer. In other words, the person who has the opinion or impression is put in the dative case:

• mér finnst = I think / I find / it seems to me
• þér finnst = you think
• honum finnst = he thinks

So mér is correct here. Ég fannst is not grammatical.

Fannst is the past tense of finnast.

• mér finnst = I think / I find / it seems to me
• mér fannst = I thought / I found / it seemed to me

This verb is related to finna but is not used in exactly the same way. In sentences like this, finnast often expresses a personal judgment or impression rather than physically finding something.

Icelandic main clauses usually follow the V2 rule: the finite verb tends to come in the second position.

Here:

• Mér = first element
• fannst = finite verb, so it comes second
• brokkolíið = the subject comes after the verb

So the structure is completely normal for Icelandic.

You could also rearrange it for emphasis, for example:

• Brokkolíið fannst mér betra í dag en í gær.

That would put more focus on brokkolíið.

The ending -ið is the definite article attached to the noun.

• brokkolí = broccoli
• brokkolíið = the broccoli

In Icelandic, the is very often added to the end of the noun instead of being a separate word. Since brokkolí is a neuter singular noun, the definite form here is brokkolíið.

It functions as the subject of the sentence, so grammatically it is nominative.

A useful thing to notice is that with finnast:

• the person experiencing the opinion is in the dative: mér
• the thing being judged is the subject: brokkolíið

For many neuter nouns, nominative and accusative look the same, but in this sentence brokkolíið is understood as the nominative subject.

Because betra is the neuter singular form of the comparative adjective betri.

The adjective góður has an irregular comparative:

• góður = good
• betri = better

But comparative adjectives still have to agree with the noun they describe. Since brokkolíið is neuter singular, the correct form is betra.

So:

• masculine/feminine singular: betri
• neuter singular: betra
• plural: often betri

Because en means than in a comparison.

The sentence contains a comparative adjective:

• betra = better

After a comparative, Icelandic commonly uses en:

• betra en... = better than...

So í dag en í gær means today than yesterday, or more naturally in English, better today than yesterday.

Because Icelandic, like English, often leaves out repeated words when they are already understood.

The sentence is short for something fuller like:

• Mér fannst brokkolíið betra í dag en það var í gær.

But that fuller version is heavier and less natural in this context. The shorter version is the normal one.

English does the same thing:

• It was better today than yesterday.

You do not need to repeat the whole clause.

These are very common fixed time expressions in Icelandic.

• í dag = today
• í gær = yesterday

Historically, í means in, but in modern Icelandic you should mostly learn these as set expressions. Similar examples are:

• í morgun = this morning
• í kvöld = tonight / this evening

So although í has its own meaning, in phrases like these it is best to treat the whole expression as a unit.

Yes. That would also be natural, but the nuance is a little different.

• Mér fannst brokkolíið betra... = I thought / felt the broccoli was better...
• Mér líkaði brokkolíið betur... = I liked the broccoli better...

The version with fannst focuses more on your judgment or impression of the broccoli's quality. The version with líkaði focuses more on your liking or preference.

In many everyday situations, both could work.