First person RPG? 0-2 companions.

Top down CRPG? 3-5 companions.

Objection!

There's a bunch of games designed to have multiple party members, but also allow for just one. For example, the Legend of Grimrock games, which, at least for me, are a lot more enjoyable solo. But maybe I'm just a weirdo who likes to play games in unconventional ways...

One thing to note, however, is that such a game is more difficult if you play as only one character, and some games (Bard's Tale 3, for example) can't be soloed.

If a game is easier with only one character than with a full party, then I consider that game to have a serious flaw. Examples of games with this issue are Final Fantasy 2, Ultima 4, and Hoshigami, but for different reasons. (In FF2, evasion level grows faster when you solo, resulting in you becoming unhitable; in Ultima 4, enemy party size scales with your party size, making combat much faster with only one character; in Hoshigami, one level makes a big difference, and a solo character gets much more XP.)

See my reply to Austrobogulator's post.

This is probably my sweet spot as well. Again, it's funny you mention 4 - my first thought to this question was that I liked 3 - 5 (with 4 hitting that average spot on).

I too like hybrid characters, but the min / maxer in me (thought probably not nearly as bad as some ;) ) makes sure that I'll only insert a hybrid character if my party allows for it. In other words, let's say a game allows only 3 characters - I'll probably have a hard time playing a hybrid character if I NEED the typical "tank / fighter" "rogue / damage" "mage / face" character. BUT if the game lets me keep the needed core and have an extra character or two, I LOVE playing a hybrid (and most likely a "strange" class as well). To put it in D&D terms - it's great to include a Druid type class, or play a Kensi - spelling? - but hard to do that if the Kensi is your main fighter and the Druid is attempting to be your healer / fighter / mage in a small party - but if your party lets you slip in a less traditional class or two I LOVE getting these into my group!

When a game is tightly coded / the gameplay is dictated a bit by the encounters I feel like there's a bit of room to make a 3 character party fun. Likewise a game geared toward 6 characters, if well implemented can give a lot of variety without starting to feel cumbersome or overcrowded. But this take a bit of skill on the part of the developer.

I think my favorite parties to play in games are those that 1) allow me to included the "needed" classes 2) let me sneak in a character class or two that I'm super interested in that might not be otherwise viable if the max party size was smaller and 3) didn't start to feel cumbersome or overly hectic in combat.

Totally subjective I know, but a fun topic to think on on a late Saturday night! ;)

Turn based RPGs in general make larger parties more comfortable than real time/action RPGs. In turn based games each unit serves a certain task and is managed per turn, in real time games however you must manage all at the same time and often is better to have just a few versatile characters than a whole army.

Six characters plus two summoned in battles, like in LoX.

One more than the class archetypes the game uses. If the game for example uses a tank/healer/dps system (even if multiple classes can fill multiple roles), the ideal party would be 4. One of each archetype, plus one more to fill gaps. Can go with 2 more than the archetypes, but it does start to get messy after a point.

In Baldur's Gate and Icewind Dale I like to have :

2x Melee characters (fighter and barbarian)
Rogue
Wizard gandalf-ish leader
Healer

Sometimes I relent and add another magic user, like a sorcerer or druid. But overall I prefer to keep it to five, so that I get a bit more experience per member compared to a full party of 6.

Ideally, 16 or 32. It should always be a number that is a power of 2, because everything should always be a power of 2.

8 is not enough, and 64 is too many. Not because it is too many party members but rather it is too many spells with special effects on-screen at once which would raise the system requirements and also make it impossible to find my mouse pointer at 2560x1600 unless the game allowed mouse pointer scaling which almost never happens due to stupid programmers that assume everyone is using a monitor made 1500 years ago.

So yeah, definitely 16|32!

84.

I always found it annoying that there was an artificial limit on the number of people in my party.
"Oh no, a new person came, so now I have to say goodbye to one of my old companions. Why don't you magically teleport to that old inn from a couple towns back, and wait there?"

It doesn't matter for me at all. I do, however, think that the party system should make sense. So I prefer games where I can either build a full party by myself and play with them without any changes in between and so I can really role play them, make decisions based on what they believe and so on or I can recruit various party members during the game but they should have some personalities, objectives and enough backstory to allow me to role play them (Baldur's Gate is a good example). The game that has non customizable party at the beginning works too as long as the personalities of party members are well done. I don't like games with recruitable one-dimensional NPCs which you replace as soon as you find somebody with better stats (MM8 is a good example).

3-10

At least three because I want to specialize at least every one a bit (melee fight, distance fight, magic) and at most 10 because otherwise it becomes a bit tedious. I guess 4-5 is optimal for me.

4-6 is my preferred party size, it's small enough to remember each character's abilities and what-not, as there's usually a gap of several days in-between my gaming sessions.

Typically I'd want at least:
1x melee warrior-type
1x healer-type
1x ranged warrior-type
1x magic-wielder in offense

The rest can be whatever sounds fun.

Most JRPG's I've played had a 4 or 5 character limit, so that's the number I'm comfy with. (4 is more conventional than 5) When Final Fantasy 7 and 8 brought the party size down to three, I felt constrained. A size of 4 generally gives you enough room for the typical Bruiser/Nuker/Healer roles with an extra slot reserved for the jack-of-all-trades to fill in the blanks.

This made me laugh, not sure how serious you are but I agree, I like big parties and I cannot lie ;)

Also this. I have six party members, I can use three or four but I occasionally fight groups of 8 enemies. Why can't I use my full party!
That's one thing I like about FF V, you have four characters and four slots, you never have to swap characters in and out.

I like Tactical RPGs where you can use loads of characters at once, because I like the feeling of levelling up characters and progressing their skills but if you're talking a more traditional JRPG then I like the party to hold as many characters as are in the game (especially if you don't share XP)