How to prioritise ideas?

With so many ideas on the table, how to choose which to work on? With zero scientific aplomb, I decided 3 is a good number of ideas to be working on at any one time. But which 3 would require a little more thought...

With a little help from a friend (thankyou Jon) I received the suggestion to create a grid as follows:

1. list the ideas
2. list the variables that would help determine successful candidates
3. score each idea for each variable
4. generate a weighted score
5. pick the best 3

Choice of important factors is perhaps personal, I have chosen 4:
1. Money - chance it'll make loadsamoney! Assuming it works.. see #3
2. Fun - will I have fun trying? This sort of includes satisfaction, interest, social etc
3. Product viability - can the product work?
4. Market viability - would anyone want it?

I then decided that two weighted scores are needed:
"survival" - the chance that the product will launch, and
"enthusiasm" - the chance that I won't get bored and give up
and that I would select one idea based on "survival" and two based on "enthusiasm"

So here's how the grid panned out:

Invention	Money	Fun	Product viability	Market viability	Weighted score 7355 "survival"	Weighted score 3722 "enthusiasm"
Kiteflyte	10	10	1	1	5.0	7.4
Napsec	7	3	3	8	5.3	4.6
Kruba	1	7	5	2	3.1	4.7
Starmorz	3	7	7	5	5.0	5.9
Chatstats	2	5	5	3	3.4	4.1
Wheg	4	8	7	5	5.4	6.6
Munchmuch	6	9	4	7	5.9	7.4
Bioalarm	3	4	9	5	5.0	4.6
SysEntrop	3	7	2	4	3.5	5.0
MiniMilk	8	6	2	6	5.3	5.9
Proffa	3	6	4	2	3.3	4.5
Compbox	6	6	9	4	6.0	6.1

So I have selected the following 3 products: Kiteflyte, Munchmuch, and Compbox.

(these names are just labels which of course may change)

These three ideas will now move to the R&D phase, whilst the rest will sit on the shelf. There will be a review every month. The overall process might look something like this: