I am almost throuh playing MM2. The scaling at first is not a problem, but later in the game the game gives you monsters that are near impossible to kill.
*Spoiler*
*Spoiler*
Thankfully I broke down and nabbed the +1000 Hp event and was able to last through it.
*End of spolier*
My question is does MM3,4,5 and 6 also have the feature of giving you new monsters baseed on your lvl? Or is monster appearance based solely on what area you are in?

Nevermind, I guess E2 in MM2 is just THAT tough!

As far as I know ther is NO autoleveling at all in the Might & Magic Series. Well i´m pretty sure about that. You can consult the monsters statistics in several FAQs/Walkthrougs/guides around the net, and they are fixed throuhgout the game, no scaling. Simply there are harder monsters as you advance in the game.

I recently beat MM2, and I also found that encounters did indeed scale somewhat with the level. For the most part it did so by adding ridiculous numbers of the last monster type. In general it meant I had to hold down ctrl-a to blow through the many creatures. Most of them would run away or I'd one-hit kill them. Mind you, at this point I was over level 100.
*spoilers*
So yes, they scale, but no, they don't really get much more challenging. If you are able to kill the ancient dragons, such that you got the big HP boost, then you can handle most any battles. The biggest test will be the dungeon in Square Lake. If you can't handle it, then you just need more levels. I found the elemental planes, the dragon cave, and the Cuisinarts (in B2 I think?) to be the best XP at that stage. I also had 100 in every stat via the various boosts available throughout the game. The circus in particular was helpful. Lloyd's Beacon is your friend.
edit: fixed typo

I've played through the whole series before (except IX), and what Viktar said is pretty much correct for MM1 and MM2. The rest of them, though, will be based on the area you're in.

Well, op was asking about new (different) monsters based on your level, the answer still being NOT.

Thanks for all your answers.

I'd disagree with that actually. I found that random encounters in most any outdoor area could result in a fight with much more difficult creatures when at a later level. For example, wandering in say, B2, at a relatively low level like 10, you could have a fight with some Inept Wizards, a couple of Jugglers, and a handful of Screaming Pods, or something like that. Whereas a random encounter in the same area at level 70 could result in several Dinosaurs, Slashers, and then like 100+ Cripples. At that kind of level the fight is not challenging, but there is indeed monster scaling with levels.
I think this scaling is probably more effective in the levels 20-30 range. The fights would be considerably more challenging. But my experience was that once I got to about 20-25 I found a way to gain levels at a ridiculous pace. I think once you get beyond 50ish the game is a little skewed and becomes "too easy".

Might and Magic I and II the random encounters scale, but the set encounters don`t, and there are generally quite a few set encounters around the place.