Try FlightGear, it's an open source alternative to MSFS, runs on both Windows and Linux and is free to download (its about 80Mb). Check out
www.flightgear.org
You need a half-way decent graphics card though anything older than 3-4 years prob just won't do.
The flight models are much more realistic than anything Ive found in MSFS, though to be honest I ve only ever flown a PA28 and C152 for real. I believe this is due to a) better flight models and b) higher frame rates, especially when it gets interesting like in the flare.
Being open-source its under active development (currently at ver 0.96) and there is an enthusiastic and very helpful community mailing list. Details on the website. There are AI aircraft and ATC though not yet at the sophistication of MSFS. The basic download has scenery for ~100miles around KSFO and the rest of the world is available for free download too. Moves are afoot to integrate MSFS scenery too.
I agree with other posters that simming in general detracts from real flying and I don't really think its a Good Thing for the 1-20 hr PPL student. Excellent for the 0 hr student cos it keeps them interested and for the more experienced its good for radio and nav procedures.
Check it out, all it will cost is the download and some disk space. All joysticks, pedals etc can be made to work with it. I use a Saitek Evo and the pedals from a MS Sidewinder racing wheel. Bit of a hassle cos I have to have the wheel connected too but worth it unless you have a tiny desk. I think it would be feasible to use the wheel as a nose-wheel tiller on the big boys but I haven't got round to setting that up yet. After all my priority is to get a PPL on a PA28-140. I'd love to move up to a yoke and 'proper' pedals but that represents about 90 mins real flying.