It's cool, dude.
I'm admin here and I'm talking about it. So long as you don't post links to ROM sites, you're ok to talk about stuff.
The DS titles and the GBA titles are good in terms of gameplay. Don't skip out on them due to other opinions. The bottom line is, as far as gameplay and music, they are topnotch titles considering that they're handhelds. Their only downside is that they copy the same "Metroidvania" formula that Symphony of the Night uses. If you like Symphony, you will probably enjoy those titles as well.
Here are the titles according to a chronological (but loose, as some games are not canon) timeline, as well as my numerical review on them (1 to 10, 10 being best).
The numerical value is as a game, as a whole, not as a "Castlevania" game.
I'm not familiar with my years, but I'm sure people will correct me on this (as well as disagree with my general ratings of the titles).
1047 - Castlevania: Lords of Shadow (PS3/X360) - 8.0
1094 - Castlevania: Lament of Innocence (PS2) - 7.5
1450 - Castlevania Legends (GBC) - 6.0
1476 - Castlevania: Dracula's Curse (NES) - 9.0
1479 - Castlevania: Curse of Darkness - 7.5
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14?? - Castlevania Pachislot 1 and 2 (currently unplayable)
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1576 - Castlevania: The Adventure (GB) 6.5
1591 - Castlevania Adventure II: Belmonts' Revenge (GB/GBC) - 8.0
16?? - Castlevania: Order of Shadows (Mobile) - 5.0
-----1691 (all)
Castlevania (NES) - 8.0
Haunted Castle (Arcade/PS2) - 6.0
Vampire Killer (MSX) - 6.5
Castlevania Chronicles (X68000/PS1)- 8.0
Super Castlevania IV (SNES) - 9.0
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1698 - Castlevania II: Simon's Quest (NES) - 7.5
1748 - Castlevania: Harmony of Dissonance (GBA) - 7.5
-----1792 (both)
DraculaX: Rondo of Blood (PC-Engine) - 8.0
Castlevania: DraculaX (SNES) - 7.0
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1797 - Castlevania: Symphony of the Night (PS1)- 8.5
18?? - Castlevania: Order of Ecclesia (NDS) - 8.5
1830 - Castlevania: Circle of the Moon (GBA) - 8.0
-----If you play Legacy of Darkness, it includes Castlevania 64, plus improved gameplay.
1844 - Castlevania: Legacy of Darkness (N64) - 7.5
1852 - Castlevania 64 (N64) - 6.5
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1917 - Castlevania Bloodlines (Genesis) - 7.5
1944 - Castlevania: Portrait of Ruin (NDS) - 8.0
2035 - Castlevania: Aria of Sorrow (GBA) - 8.5
2036 - Castlevania: Dawn of Sorrow (NDS) - 8.0
-----Games not set in a specific Time, but presumably in the future
10000 (LOL) - Kid Dracula (NES, GB) - 7.5

?? - Castlevania: The Arcade (Arcade) - Unplayable (unless you can find a cabinet in the USA)

?? - Castlevania Judgment (Wii) - 7.5

?? - Castlevania: Harmony of Despair (X360/PS3) - 7.5