... First, it's not porting unless they have the original source code- which you cannot get for any games but open-source games. Even for games that have been made free (GTA 1 and 2 for example) you CANNOT get the source code. Thus you cannot port it. Thus to get it on the DS it has to be RE-MADE, as in COMPLETELY REDONE. In re-doing it you have to create software which would (and did) take a professional company with hundreds or thousands of employees several YEARS to make. Then you can call the game created by the process a 'clone' or a 'remake'.
But to call it a port is just bullshit, excusing my language.
Oh, and to wiowao- sure it wouldn't take three years to PORT a game (which, once more, can only be done with a select few games), but it sure as hell would to REMAKE that game. There are basically no developers willing to spend several years (of full time work) remaking a game for no money and for a system which would be obsolete and unused by the time the game was released. (Keep in mind that I am talking about modern games, much older ones are a little easier because there is no need for excessive textures, models and a complicated 3D engine.)
And yes, I am aware of 'Bob's Game', but that game was not a remake, it was his own IP- this is why he feels he can make some money by selling it. He wouldn't remake a large game because he would not have any rights to it and thus could not make any money on it. In fact, remake projects are often shutdown by the companies owning the IP.
If you want further evidence of why remaking a game is hard- look at
OpenMW (a remake of Morrowind). It's taken years for it to get anywhere (leaving it a little out-dated), and that's with many people (and a community) working on it. Plus it's open-source, meaning that the market for it spans across every operating system. It is a large project, and every system (possibly including the DS, if it can be scaled down enough) will later have the gane ported to it. You just don't remake large games for a console. They are made for Windows or Linux first, then ported. Go onto another forum, get a game remade, then come back here to talk about porting it to the DS.
In short, almost nobody on this forum (who has the ability to) is interested in remaking a modern game exclusively for the DS. And those who are (if any), are not organised enough or are simply not interested in the same game as the others.
EDIT- oh, and just to clarify- a modern game is pretty much any game released from the Nintendo-64 onwards.