I like Alien Skin Blow Up and Neat Image Pro
I use Photoshop. First enlarge it using 10% increments, save at each increment, if it looks pixalated blur it and add some grain. It takes some time to get it right but in time its worth it.
On images with geometrical structures (e.g. architecture) it might makes sense to use a special software. Usually, I think the results shown by the makers of these products are wildly exaggerated, IMHO.
Use photoshop - image size - bicubic smoother
i find photoshop to be the best enlarger
From my own experience.
Print images have the same resolution - which is a multiple of the physical resolution of the printer.
If the printer is Epson - 1440 DPI ... then prepare the image for it to be 1440, 720, 360 or 180 DPI.
Then exclude unpredictable transformation in the printer driver or RIP processor.
For those saying "Photoshop" you really aren't responding to what the OP asked for.
You don't just click photoshop and you are done... you have a process that you follow. Why not explain that out? That is what the OP asked for, your WORK FLOW.
To those that did put your workflow of using Photoshop in your response, thank you very much!
Best one in the market AKVIS Magnifier
I have used Photoshop's plugin called Perfect Resize 7 (before it was called Genuine Fractals) and the results are just perfect
Thanks for sharing
The crucial part is to get rid of artifacts and noise prior to enlarging.
Depending on the original I use either Nik's Dfine, AlienSkin's ImageDoctor or/and Imagenomic's Noiseware Pofessional or Portraiture, then go for a decent enlargement - which could be any of you mentioned.
There is no one blessed solution, the way you chose greatly depend on the original image at hands.
I also like this one:
OnOne Perfect Resize 7.0.7 Pro
Password as usual for this site.
all this time searching, honestly I haven't found the 'perfect' jpg enlarger in the market, but I thing Genuine Fractals is okay. you won't get the same enlargement quality like in Hollywood movies, but, it'l get the job done
I alwasy use Photo Zoom pro and the results are very pleasing.