Questions about Half-Life games

[OC101]

1. Is Source games more popular than HL1 games?
Are they worth getting over the older ones?

2. If I want to play CS:S, DOD:S, TF2, HL2 multiplay what should I buy is the most cost efficient way? It is a little confusing. All I needed to play all HL1 mods was a key of HL1.

[grayg]

1. Is Source games more popular than HL1 games?
Are they worth getting over the older ones?

These days Source games probably are more popular and in my opinion you can't go too wrong getting HL1 type games or HL2 type games. Though my personal favourite still remains the orginal Half-Life.

2. If I want to play CS:S, DOD:S, TF2, HL2 multiplay what should I buy is the most cost efficient way? It is a little confusing. All I needed to play all HL1 mods was a key of HL1.

That's because they are no longer simply fan made mods, they are developed by Valve themselves and thus they have to be purchased. You can often get some games bundled in with others, but otherwise yes I would agree with you about it being confusing as they re-release things in different deals etc.
Maybe you should check out the "Source Premier Pack" and the "Valve Complete Pack" on Steam

[Malpine Walis]

You would do well to get the Orange Box. You get a whole bundle of games that if you tried to buy them separately would cost like twice as much. You will probably play them all eventually as they all kind of mesh together with common elements (except for TF2 but even so...).

Also, with a bit of googling, you can find instructions on how to open the maps from one game in another. Granted, there is not a whole lot of use for the .357 in Portal but using the portal hand held apeture device in HL2 has some potential.