Can you tell me how it's different? I love S2 but it is just on the cusp of being a little too old school. I grew up with an Apple \\ so don't get me wrong, I love nostalgia, but only to a point.
Here's a list of all the differences in between the 2 games:
Only one graphic set for all the people (medieval), the fractions are only differentiated by the colors of their clothes and the one on the flags, no no-man's land in between 2 fractions as the landmarks limitiong each one's territory are just black and not in the respective player's colors.
There actually is a campaign, but it's more of a loose sucession of 30 Maps with increasing difficulty. Each one of these has it's own password to skip them later on. There are also 6 training missions which explain you step by step the different buidings and an unlimited amount (well 10^16*9 to be precise, more than you'll ever be able to play in your lifetime) of skirmish maps in 9 different sizes.
On skirmish maps, you can adjust exacly how everybody will start the game in therms of materials, reproduction rate and, in case of AI opponents, their overall intelligence.
Also, SVGA is actually an option, but all it does increasing the screen resolution from 320x200 to 640x480 without increasing the size of the sprites or higher-res buildings, which means everything becomes really tiny. Only advisable on big screens.
There are over a dozen ennemy leaders, each with their own tactics and personality.
Waypoints work differently in between both games. In settlers 2, you have to put as many flags as possible to increase the number of portes. In the first game, the number of portes got adapted depending depending on traffic. aAlso, no donkey porters and only one porter (or any other settler by that matter) can walk to a flag at a time, which means that roads tend to become very congested if you don't plan very far ahead.
You can put pathways trough forrests, but still no flags or buildings. There are also only 2 building sizes.
All leaders start as ennemies by default. You also don't need to conquer them entirely, if you got a 75% lead in Military power and Land size over all the other leaders combined, you're the winner by default.
The maps wrap around, and can also be much bigger than Settlers 2 maps despite lacking seafaring ships. On the biggest maps you can actually settle for 10 hopurs before even making contact with one of your opponents.
Fishermen never run out on fish, as long as you dont overexploit a lake (there are only lakes, no ocean around the maps).
Butchers, Mills, Bakerys and Carpenters are way more productive than in Settlers 2, meaning you can build a lot of Farms and Woodcutters to "feed" them. Farms also need a lot of Space southwars as they plant something like 20 Crop fields if they got enough space (and need them, too). On the other hand Forresters, Builders and Fishermen work slower. Diggers also need a lot longer to flatten terrain for big buildings.
There are less transport options, less storage options, but more options for the minimap. Combined with the bigger maps the latter actually becomes quite useful to check out your whole kingdom.
There is no set spot where you start your castle, you can choose to put it wherever you want. The Geologist will tell you about about the ressources in the vincinity (in case of granite, he only means what's actually underground to mine) before you set down. This also applies to your opponents, so choose extra wisely. It ain't very interesting to start right next to a much stronger AI opponent.
You can see how many soldiers are garrisoned in a military building by the height of their flag. Very useful since generally you run out of soldiers on bigger maps really quickly, which forces you to micromanage your troops early on. Also due to the fact that the maps wrap around, since it means that your opponents will be all around your little empire.
Not yet implemented in that game: Catapults, Breweries, Fountains, Donkey Breeders, Harbors, scouts and their towers (the map is fully revealed) and hunters.
The game is much more challenging because it's not forgiving you any errors you make starting the third map, especially concerning pathbuilding and later also soldier allocation.
Hope I didn't miss anything out ;)